From my own viewpoint as somebody living in Europe but not in the UK (though I lived there for over a decade), there are a lot of people here from places like the US and the UK who think they're Leftwing and yet are just parroting the slogans of the mainstream "supposedly left-of-center whilst in practice hard right" parties with authoritarian tendencies in those countries (Democrats in the US, New Labour in the UK).

People in countries with VERY to the Right Overtoon Windows have been deceived into thinking they're leftwing all the while claiming (again and again, for decades) that leftwingers have an obligation to vote for Hard Neoliberals to stop the Fascists and looking at other human beings and them seeing first and foremost as members of identitarian groups based etnicity, gender or sexual orientation (the exact same perspective as the Fascists) who they claim should be treated differently from other groups whilst calling with no irony that their desired differentiated treatment based solely on etnicity, gender or sexual orientation is "positive" and "fighting for equality" even whilst avoiding the whole "for all without looking at skin color, gender or sexual orientation" Equality part of the real fight for Equality.

There are tons of infighting in the Left, but what we see here in Lemmy is mainly not that but rather liberals from Anglo-Saxon nations thinking they're leftwingers and attacking actual leftwing ideas.

We can definitelly see some infighting between Communists, Socialists, Anarchists and Social Democrats in those places where hexbear hasn't been blocked but the main supposedly leftwing "infighting" we see in Lemmy (especially in the lemmy.world communities) is right-of-center (neo)liberals from English-speaking countries vs people with policy preferences mainly fitting the Social Democrat spectrum who aren't even ideological Social Democrats.

(All of this IMHO, of course)