to add to that, Lemmy currently does not handle site bans well if it's not a home instance ban, as instances don't keep track of which other instances have banned which users. this should get better with 1.0 though, as a PR to improve that was recently merged.
for now, there is a band-aid solution that federates community bans for all communities local to the instance the user got banned from, but that only includes communities that the user previously participated in, so they'll still be able to participate in the local copies of other communities from the instance they're banned from, it just won't fully federate out.
slur filters are a commonly used method on lemmy to deal with certain types of spam.
there are lots of spammers posting links to blog spot subdomains all the time, i think there were at least two new ones just today.
unfortunately, the amount of malicious links (random spam posts) to blog spot significantly outranks the amount of legitimate links, which is likely why this was added to blahaj's slur filter.