Tankie's original use was for British communists who supported Soviet military expansion. In the modern sense, it is used to describe communists who are authoritarian-apologists. For example, a communist who romanticizes the Soviet Union or makes excuses for the Uyghur genocide is a tankie. I've also seen it stretched to include militant anti-capitalists, or more commonly, "militant," anti-capitalists who call for violent resistance to capitalism from the safety of a keyboard.
Democratic-Socialists are not tankies. Socialists are not tankies. I don't even think most communists qualify as tankies. Criticizing Democrats does not make you a tankie. Condemning Israel's human rights violations does not make you a tankie. Voting third party doesn't make you a tankie. I see this term used here every day, but never correctly.
Again, the definition of the word changed. It’s how these things work. Now, it seems to pretty much describe trendy socialists that pick a hot button single issue to be upset about- troll the internet with noses about it, and pretend they actually could have point on a map to where said events are happening six months ago.
Yeah, I don't think most people in this community would agree with the definition you just laid out, and as I said, this community is already misusing the word. What you're describing is closer to the, "dirtbag left," than anything else. You're stretching the definition so far past, "pro-authoritarian-left," that it's ridiculous. It would be like if I started calling Biden supporters, "Bernie Bros," and said the definition had shifted to include any supporter of a left-of-center male candidate. It's so incorrect it's made the word meaningless.