No, I believe you should discuss any mass re-tagging. `{{PossibleSynonym}}` has not been used on wiki yet either.
Yes, I have documented it myself osm.wiki/Proposal:Crosswalk_clean-up#Crosswalk_as_lines
Another use for this is allowing regex or prefix search of `footway=crossing*` for all crosswalk parts. `=traffic_island` would need an union, and excluding non-crosswalk traffic island walkways.

It would at least need to be distinguished by `traffic_island=` `=crossing` vs `=platform`

Where has this been discussed? I don't favor `=traffic_island` as it may be used for the `=footway` connecting to transit platforms.

First of all, `building=terrace` must be wrong. It's used on the entire row, not individual houses, which is `=house` + `house=terraced`
Regardless, these debates really shows `=house` + `house=` being superior. Leaves arguing the attribute, instead of feature.

What does that mean?

It's `disused=yes` vs `abandoned:highway=` not `highway=` + `abandoned=yes`

Please don't delete, but change enclosed `building=` to `building:part=`

Please don't merge `building=` area with site grounds area. They are different

0. Please use meaningful upload comments
1. Please don't upload personal test data or similar

This should be `description=`

`name=` is for proper names, not descriptive titles. These `name=` should be official as in survey sheets.

You missed the point. The difference is whether they are physical structures, or functional activities. Unused roads, buildings, towers, etc still exist. Unused services, no longer.

`destination:ref=` is when the road only goes to that route. This is `destination:ref:to=`

1. Please don't remove Chinese from `name=` , which should be bilingual
2. If it has offices etc other uses, it should be `=commercial` or `=industrial` , not `=service`
3. `website=` is the page specific to the facility. Please use eg `operator:website=`

`disused=yes` is not Troll on `highway=`

Please use `change=no`

Please don't draw a pair of lines when there's no raised separation. Use `share_taxi:backward=no`

https://www.mtr.com.hk/en/corporate/tenders/TUE_C12003.html ?

https://mtrtungchunglineextension.hk/tung-chung-east/ ?

1. Government or official documents often capitalize a term to distinguish it. That doesn't necessarily mean it's a proper noun. You can also find many "former".
2. I said `old_name=` , not `name=`