I just removed all the few questions tagged it, and I was thinking about removing system-administration for the ~27 questions, but I didn't really want to bump all those questions. I think both of these tags should be blacklisted here, since almost every question should be able about system administration.
ok, I blacklisted
^(system-administration|it)$ from tags, and destroyed system-administration -- these are what we call "intrinsic" tags meaning they are assumed on the site, like you wouldn't tag a question on apple.se [apple] because, well, they're all apple questions.
These intrinsic tags are also checked on migrations.
Unfortunately, tag blacklisting is not one of the superpowers I have at my finger-tips. There might be a dev-tool for that.
On the other hand, I can destroy system-administration with fire.