Quite often we have situation that discussion about a specific tag results in consensus that the tag should be removed. And the removal process means that the questions having that tag are retagged and thus bumped. In some cases, this might be quite a big number of questions. (For example, when the tag (straight-lines) was created, after the discussion on meta it was removed. But in the meantime it was used in more than 70 questions. There is a recent discussion about (birthday) tag - it seems that the tag is going to stay or maybe it's going to be renamed, so actually no harm was done there - but it's another example where a tag was used in more than 100 question in the first two days after creation. And I am pretty sure it would be possible to find some other examples of tags which were used in many questions when possibility of removal was discussed.)
Question. Would it be reasonable to create a special tag tag-removed for this purpose:
- For regular users, this tag would carry nor information, it would be just a placeholder.
- Moderators could use this tag in such way that when some tag is removed, it could be merged into this tag. In this way, tag could be deleted from all questions without bumping.1 (Probably it would be useful to look at the questions first and retag at least those which are tagged incorrectly. But still this could reduce the amount of retagging and bumping.)
- Of course, if questions having this tag is bumped for other reasons, the tag can be simply removed. (But this would probably upset less users, if the question was already bumped for another reasons.
So the main advantages would be: Less work when removing tags. Possibility to remove the tags without bumping.
Disadvantages: If a process like this is made silently, it's possible that users who disagree with the change can miss what is going on. (I.e., bumping means that more users notice that something was changed.)
I will also stress that this tag would be different from the untagged tag, which is created in some specific situations by the system. In fact, (untagged) cannot be added by regular users, see here for more details: Do not allow users to tag questions with “untagged”.
1How moderators can "rename" tags without bumping is explained in detail here: Can you change the name of a tag? (I wrote rename in quotation marks, since it is not actual renaming, only merging with another existing tags.)
There used to be tag with this name also on this site: What is the role of the '[tag-removed]' tag? It is mentioned in Qiaochu Yuan's answer that: "The first meaning is its original meaning on MO... This question had a tag which was inappropriate, and that tag was merged so as not to bump the question. (That is, it's a hack.)" So probably this tag was used for similar purposes also on this site in the past. (The linked post is from 2010. I did not find a discussion on meta which lead to removal of this tag.)