Can emacs23 and its synonym emacs-23 (144 questions) be made synonyms of emacs (4413 questions)? In my opinion the former are not independent enough to make their own category of the latter because they are just a particular version of the latter.
As usual with tags including version numbers, there is a legitimate use for emacs-23: when your question is specific to that version and is not useful to someone running Emacs 22 or Emacs 24. As usual with tags including version numbers, the tag is abused by people who are merely indicating that they happen to be running that version. I favor doing a one-time cleanup: merge emacs23 into emacs, but do not create a synonym, let the emacs23 die out. When Emacs 24 becomes more common, I expect emacs-23 to arise naturally to mean “How do I do this in Emacs 23? I have a solution in Emacs 24 but it doesn't work in 23.”. In the meantime, we who answer Emacs questions should remove the emacs23 tag if it creeps back up for no good reason.
Agree. I see no reason why a particular version should be singled out - expecially, since there is nothing special about it (unlike let's say, Python 3.x vs. Python 2.x or some other similar example).
Otherwise, we might start making new tags for every new version of every software that comes out.