I’m not convinced from that comment that the user they’re referring to is a tankie, but simply put, I’d describe a tankie as the alt-left equivalent of the alt-right.
They’re not quite as violent in my opinion, but they push pro-china/russia propoganda and misinformation, and are just as self-deluded and delusional as the alt-right. I’ve also seen tankies justify Hamas’ attack against Isreal, which I find inexcusable and morally reprehensible. The same can be said of the IDF’s genocide against innocent Palestinians.
Tankies are on the fringe and are just on the other end of the bell curve of the alt-right.