Hmm. Yeah, I really don't think I like != ligature. I don't want to mistake it for some non-ascii unicode symbol, and I generally like what I type to stay the way I typed it (including curly quotes!).

Yeah, no thank you.

Also, I notice that Jetbrains Mono doesn't ligature ~= as !=, but that is what it means in Matlab. So it really seems like assumptions about language semantics is baked in to the font.

Jetbrains Mono does offer the no-ligature version.