I think mods get tired of having to deal with shit, and so anything that remotely resembles what they've removed in the past gets classified as similar.
Also many users (not mods) are rule lawyers and love to spam the report button and that can influence things as well. Like if nobody had reported this perhaps it would have stayed but then when someone did...
Ultimately this has all the earmarks that it might be a PTB, yet it does seem arguable that the mod could have been simply overeager and not paying close attention, so potentially a CLM? (Which itself is simply another form of an unintentional and low-grade PTB?)
Edit: in all likelihood, we here are putting in far more effort thinking this situation over than the mod in question did:-P.

