I feel there's been some very sus behavior coming from centuriichan and I wonder what role this sublemmy plays in unintentionally normalizing racist rhetoric
Unfortunately it's a reddit comment but it compiles a very good list of very questionable trends in their comics
There's also this one making light of colonial r*pe and drug exploitation: 
I personally don't see much difference between this covert form of racist and colonial normalization via cutesy anime characters and pebbletoss' more overt palpable webcomic form of racism (might even argue that this is worse since it has enough plausible deniability)
Curious to hear your opinions
Yes, centurii is very much 4chan "edgy humor". I didn't think this was a secret, or a recent development.
Now personally I don't mind a bit of edgy humor with the understanding that it's humor value comes from breaking the norms of common decency. It does not mean those norms should be broken outside of the joke. Sadly, we can't trust everyone to get the joke, as we see in your screenshot of the idiot railing against "race mixing" (also, that joke isn't very funny imo).
I know Lemmy is generally a bit more sensitive to this, so it was surprising to me that centurii gets posted so much. I'm not worried that it will normalize racist rhetoric, because most users here will either get the joke or think it's not funny because of the racism. You have to be a special kind of stupid to miss the joke and like the comic for the racism.
The risk is that posting edgy jokes attracts the especially stupid people, which is why I'd only do it in communities that are generally super anti-racist. Any special stupids can't help but get baited into revealing themselves in such communities, which makes them an easy ban.