Reply to Kovoschiz: First of all, thank you for the detailed comments. I attached my opinion as follows:
1. `aeroway=concourse` is invalid. The talk topic you provided is not discussed by anyone else, is not accepted, and is not used in JFK. Actually, according to overpass-turbo, this invalid tag is rarely used worldwide (only used in 2 airports)
2. According to [HKIA's official website map](https://www.hongkongairport.com/tc/map/) , T1, T1 MFC, T1 SC, SkyPier, and several car parks are marked as independent buildings with names in the same style. Of course, I can imply from the T1 prefix that MFC and SC are parts of the T1 system, but according to current practice, they could be treated as separate `aeroway=terminal` buildings like most satellite concourses in the world do, for example [LAS T1 - Concourse D](https://www.openstreetmap.org/way/143887543). If they are different buildings, they can be separate `aeroway=terminal`s.
3. I understand and support that you are trying to relate these `aeroway=terminal`s to the T1 system, but there is no guide on wiki to create an `aeroway=terminal` but not `buidling=*` multipolygon consisting of multiple terminal buildings, and it seems to make no sense to me personally. To my knowledge, a Site relation is a good choice to describe the relations of several objects which together have a single identity according to [wiki](https://wiki.openstreetmap.org/wiki/Relation:site) , and most values of "site=" are not documented, so I create a non-standard one following the practice. But I realize that `aeroway=terminal` can be directly used on the Site relation, just like `amenity=university` site. Would that be a good choice to change the relation to `type=site` + `aeroway=terminal`? And should the car parks be included?
4. I agree that `building:part=` is not a good choice. `aeroway=concourse` maybe 
 a choice for the 5 concourses within the T1 main building, but it's not approved or documented. This issue could be explored.
5. Lastly, I was not trying to "remove tags that you don't understand". I fully understood the intention here (as described above) and the tags added, and I removed those tags based on my understanding. Please don't blame and keep calm to discuss.

Open for discussion.