I just answered a question about TeXShop and I noticed that there's no TeXShop tag. Before creating extraneous or discouraged tags I went over to the tag CW post on meta and it says that "Formats, tools, compilers, etc." should get tags. The examples given are
[bibtex], which are two compilers, one format, and one external tool, I think. Editors aren't listed here (there is an
[editors] tag though), but MikTeX and AucTeX do have tags.
In the course of preparing this question I've pretty much decided that an editor is a "tool" and each should get its own tag. But I thought I'd get a second opinion.
Edit My comment to Martin's answer explains my rationale for creating the tag, which I've gone ahead and done.
This brings up the topic of what tags are for in the first place. The top-voted, accepted answer is that tags are for finding questions you can answer. If so, people will get more use out of a tag for a specific editor that they know well, rather than all editors.