if you see people doing this shit, report it. its against the terms of service.
genuinely. copy the link to the fic or series, and then scroll down to the bottom of the page:
click on policy questions & abuse reports which takes you to this page:
if you scroll down, youll be able to report the fic right there but you can also check for yourself that its against ToS
all you need to do is explain that theyre deliberately mistagging things which is just not a thing on ao3 because its an archive.
by posting your fic there, ao3, has the right to manually recategorise tags. its in the ToS:
you cant deliberately mistag stuff on ao3; it is an archive. you cant tag for reach, and this is likely gonna get pat tag wranglers because they deal mostly with form not content of tags and if theyre tagging for reach, its gonna be the more popular tags.
so report the fuck out of them for it. most likely, their fic will just have tags adjusted and their account will be fine.
and if they keep doing it and get suspended for it, its their own damn fault.
also thats not even getting into the fact that mistagging fics is kinda antithetical to their goal of reaching more people because youre not reaching the people who want to read your fic?