I encountered the standard and am wondering if it's remotely a good idea. It seems to imply any standard... should it exist? or perhaps should we disallow it and encourage people to specify the standard they're asking about ANSI, ISO, POSIX, LSB, etc.
I agree, the tag of standard seems kind of useless. It would make more sense to have the actual names of standards as tags rather than this high level tag.
While there are many unix-related standards, by default, “standard” in a unix context refers to the POSIX/Single Unix standard family. When it doesn't, other tags should guide towards the applicable standard.
I think the standard tag is useful because quite a few askers don't know what standards apply in a given situation. standard is a perfectly reasonable tag for questions such as How stable are Unix shell "stdin/stdout APIs"?, Which are the standard commands available in every Linux based distribution?, What is not shell specific?, …