I don’t think that’s an argument from authority. “Experts have been discussing X without reaching a conclusion for a long time” is a premise from which a reasonable argument can be made for the unlikelihood that an off-hand comment on HN has solved X. Argument from authority doesn't take that form though the two do have invoking authorities in common.

It's dangerous to go alone! Take this! https://en.wikipedia.org/wiki/Epistemology

If you’re not interested in engaging in a discussion, why bother replying?