Retagging counts as editing (I don't completely agree with this, but the line has to be somewhere), and edits should move a question to the top of the home page. Questions are not always closed because they are completely wrong for MO. Closed questions can often be fixed up to be good questions. For these questions, edits should make them more visible so that the people who can vote to reopen them (3000+ rep users) can re-evaluate them.
]]>If somebody uses terrible tags that just shouldn't exist, ask a moderator to merge the terrible tag into [tag-removed] (for example, I used this technique to remove the tag [newbie]). This has the advantage that it doesn't bump the question.
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