I think people are concerned because both lemmy.ml and lemmygrad.ml are operated by the Lemmy developers. At a minimum, that means I'd prefer to avoid communities based on lemmy.ml and favor servers with less spicy admins.

There is, however a popular idea that software tends to reflect the values of its authors. Mastodon seems to be "Twitter for nice people" or thereabouts. If Lemmy is "Reddit for militant communists", that's a problem for attracting an audience beyond militant communists because most people don't want to talk to them.

No proof, I just heard about it. A buddy and someone on reddit told me about "tankies on lemmy" which I dismissed as drama at first, then I heard it's actually the main devs too, then I did a quick google search and search on lemmy here, it seems universally agreed upon at least in those threads from what I can see.

It's a term mostly used to distinguish left-authoritarians from left-anti-authoritarians, particularly in the context of the cold war West. 'Tankies' notably tend to defend their left-ideology by talking up major authoritarian or totalitarian regimes (like Stalin's or Mao's) that also called themselves Socialist (despite such claims being problematic in doctrinaire terms). Originally used to describe the self-proclaimed communist/Stalin apologist, the modern tankie supports pretty much any authoritarian regime that opposes the West