really suspicious edit on node/530718006: was tagged as a cliff (on a node?) and you changed the name and added an istat_id, a place tag and more information, including a drinking_water tag? What is it? Please fix

please use more explicit changeset comments, for a hint how a good changeset comment might look like, see here:
osm.wiki/Good_changeset_comments

you did remove the amenity tag and added an aeroway tag. There wasn't an aeroway tag before and after you added it there is still the same amount of tags, so clearly you have removed a tag. There is no "switching", a tag modification would be to change the value for a given key, not remove a key and add another one

You have inserted every hall as its own philharmonic theatre and tourism attraction. Both does not seem corresponding to reality. Maybe the Parco della Musica can be considered a tourist attraction as a whole, certainly not every single stage as its own. Please fix.

this is an undiscussed automatic edit and should be reverted

why did you remove some tags from here? Looks like an undiscussed semiautomatic edit...

Please let's not mix tagging and a specific rendering style (like red dots for footways), but rather focus on the meaning of the tags. The "standard style" rendering is just one rendering of many, and not even the one most people are using (if you look at mobile apps based on OSM data with millions of users, like maps.me).
It is true that there aren't any landbased vehicles like cars in most of the city, but there are handdrawn/pushed pushcarts and barrows, and maybe there are some emergency vehicles besides waterbased ones? I would like to keep the tagging as consistent with the rest of the map as possible (as it is an Italian city I believe it should before all be consistent with other Italian places. Not admitting cars into the historic city is not so special as it might sound, there are other places which have similar limitations, due to spatial constraints).
I suggest we leave this particular changeset discussion and move to the wiki or a mailing list, e.g. tagging or talk-it. In the wiki there is already the Venice page, which is practically dead currently:
osm.wiki/Talk:Venezia
If things get too long there, we might later move it to a subpage.

this import was not discussed

the license of the imported data is not compatible, as it is cc-by 4.0

see also https://lists.openstreetmap.org/pipermail/tagging/2017-April/032245.html

another changeset where parks have been changed to garden where it doesn't apply, see also https://lists.openstreetmap.org/pipermail/tagging/2017-April/032245.html

this is an undiscussed automatic edit and should likely be reverted

you also deleted the steps on the metro garbatella parking. Please be carefull and don't delete stuff that is there. I have used these stairs today.

you should not delete ways and redraw them, because this obfuscates the history, better modify the existing structures. You also introduced dual carriageways where there is no physical separation (parking access road)

ho notat che hai cambiato parrechi parchi in giardini, qual'è il criterio? Per me questo "giardino" in OSM è un leisure=park
Quale sarebbe il garden:type da applicare qui?

btw.: you are the only one seriously engaging in a discussion about this, for which I am grateful, but it also illustrates my point that there isn't an active mapping community in Venice (unfortunately).

Hello Sputnik,
following our discussion there was some discussion on the Italian mailing list, and not for the first time ;-)
I have update the discussion page of Venice to keep trace of this discussion and former discussions about this topic. I am not sure how well you can understand Italian, but just in case, here's the link:
osm.wiki/Talk:Venezia#Pedestrian_street_or_footway.3F (maybe you can get some clue by employing an online translator if not).
I have also written a message to user:Arlas who apparently was local for some time to Venice (but now is likely not any more). Basically, from what emerged on talk-it, there aren't any active local mappers from the historic centre of Venice, although there are some from the wider region, most of Venice mapping was done by externals. There also doesn't seem to be documentation of this "emerged standard" but in previous discussions, as you can see from the links, there were more people advocating using more than one highway value than there were for using only pedestrian.
Regarding the very narrow streets and ways in Venice, the situation is not so singular as it might seem: there are similar situations in most historic town and village centres in Italy, where accessibility via steps and width de facto prevent vehicles from entering. It is common practice to use footway for this kind of "road". Clearly, calling something a "road" where the width is so narrow that not even two pedestrians can pass, is against common sense and the general understanding of the term "road". These are admittedly even in Venice the minority of ways, but lots are so small that a car would not pass if it could arrive there.
If you have a look at the documentation, highway=pedestrian with area=yes is the common way of mapping any kind of square: "A closed way tagged with highway=pedestrian and area=yes is the common way to map squares and plazas." and there is even specific mention of highway=footway for access: "Often other paths such as highway=footway will connect with the edge of the pedestrian area.", and: "For small paths which are too small for cars to pass (no real streets) use highway=footway instead." from highway=pedestrian
So I don't see any inconsistency with the intended mapping of Venice, I see an inconsistency if we map small paths as highway=pedestrian.
Mapping big roads for pedestrians as highway=pedestrian and small ways for pedestrians as highway=footway is documented and established practice. It makes the map more readable by showing a hierarchy of pedestrian ways (although for the case of Venice there would likely be an advantage of having a third class to get more distinction and to make more sensible renderings in lower zoom levels by hiding unimportant ways earlier).

Ciao, ho notato che hai modificato la classificazione del "Calle del Fontego dei Tedeschi" e del "Ramo del Fontego dei Tedeschi" da footway a pedestrian. Mi sembra una modifica strana. Ci sono stato 4 giorni fa e per me si tratta chiaramente di footway, non hanno l'ampiezza di una strada, sono percorsi più piccoli. Ti chiedo di aiutarci a ripristinare la gerarchia dei spazi e percorsi, tenendo soltanto quelli grandi come pedestrian (e tutte le aree / cortili come highway=pedestrian, area=yes) mentre i percorsi piccoli dovrebbero essere footway.

I do not object to discussions, rather the opposite, I have started one with you and on the national italian mailing list, where I have also asked about local mappers. It just doesn't look as if there is anything like a community of Venetian mappers. People on the Italian mailing list said Venice was still recovering from the license change in 2012, 5 years ago.

Don't worry, I won't continue mapping in Venice now, I was there for some days and used the time to do on the ground surveys and mobile mapping, but have left the city now. I couldn't wait to do this because I knew I would be leaving soon, and I didn't want to waist the time there without having the map benefitting from on the ground verification and modification.

As to the "emerged standard", I will repeat what I have already written above: the emerged standard for highway =pedestrian is that it describes a road. Most of the ways in Venice with this tag aren't roads in any sense, they are very narrow footways with no vehicle traffic whatsoever. Area=yes with highway=pedestrian are highway areas of any kind and size of squares, there is absolutely no problem if these are accessible only by footways, and there is no consistency problem at all if this is the actual situation on the ground, if you believe it is then please explain why.
highway=footway with area=yes would not make any sense semantically, so it is right IMHO that carto osm doesn't support it.

there is no consistency in my eyes if 50cm wide passages where not even 2 pedestrians can pass each other are mapped the same as a some meter wide road. All my changes are the result of surveys I have been doing the past days and I do believe they improve the map so I will not revert them. I think I am improving consistency by applying these changes.

If there's no wide enough way leading to a square it will indeed be impossible for vehicles to reach them, also in reality (typically you won't see vehicles in most of venetian land based ways anyway), but footway in general doesn't automatically imply no vehicle can go there (bicycles and motorcycles might be (exceptionally) permitted by access tags or might ignore legal restrictions, emergency vehicles could pass anywhere where space is sufficient, etc.)