Both methods seem to be in use, e.g. with Facebook:

facebook=*

contact:facebook=*

What does this line represent? way/303287754

Thanks. I didn't want to break things! :)

Duplicate ways:
way/515121882
way/515123264

Duplicate ways here:
way/515121896
way/515123278

Oh, that said, this line appears to be correct - townland boundary slightly off

This looks like a duplicate of the townland boundary: way/349333803

Does this road exist? way/29257244

Is this line a duplicate? way/260655142

Can you check the tags on way/512633011 ? :)

The connection between the N52 and Main Street seems to be missing. Has the layout of Emmet Square changed?

The edit to this way: way/419502785 seems to have broken the bus / cycle connection from St. Stephen's Green East to Leeson Street Lower

Instead of

bridge=low_water_crossing

would

ford=yes

be more appropriate? ford=*

When doing pedestrian crossings and other road ways, do make sure that they join up with adjacent roads. :) The geometry and Routing layers here: http://tools.geofabrik.de/osmi/ are good tools.

Is a right turn allowed from Saint Michael's Drive to the R852?

Cool

This appears to be on the wrong continent.

This one? way/444670138

I don't have a specific recollection. Importantly, it only connects to a 110kV substation at one end.

It seems to be consistent with: http://www.nienetworks.co.uk/documents/Connections/Networkmap_33kv.aspx and http://smartgriddashboard.eirgrid.com/#all/transmission-map

It may be that it is designed for 110kV, but operating at 33kV.

Note that power=minor_line is anything under 100kV.

Is Newtownards Exchange NINT a BT telephone exchange?

Fair point. I've done a quick tidy up.

I was only drawn to the area by the newly disconnected road of a previous changeset.