Update: Tag no longer exists.
There are presently two Open Qs tagged merging:
One concerns merging questions (specifically two that have since been deleted) and the other user accounts (for a specific user).
In general, where a tag is applied to two different questions it will not automatically be deleted (each causes the other to be maintained). However it seems that even a single instance may not automatically be deleted when used for WAmeta.
Another, and more popular use, for “merging” is in connection with tags, though in that sense we have tag-request whose Usage guide is at present:
This tag is for requests to replace one tag with another existing tag. It also applies to requests that one tag should be merged into another, or simply abandoned.
user-accounts whose Usage guide at present is:
Refers to user accounts either generically, or across the network.
login whose Usage guide at present is:
For issues connected with site access to Web Applications as a registered user.
and, perhaps, without Usage guides at present:
If merging is to be retained, should it apply to both “accounts” and “questions”, and if not, to which, or to neither?