I think that commenting “Great post” carries more implication that you actually mean it (or something like it) than saying “very well, thank you” when someone asks how you’re doing. It doesn’t have to mean “this is one of the all-time great posts” or anything like that, but I at least wouldn’t say it if I didn’t mean at least “this post is good in absolute terms and better than most others like it”, and Jacob is claiming that that isn’t actually so. That’s not a nitpick about conventional phatic utterances, it’s an actual disagreement of substance, no?
I think that commenting “Great post” carries more implication that you actually mean it (or something like it) than saying “very well, thank you” when someone asks how you’re doing. It doesn’t have to mean “this is one of the all-time great posts” or anything like that, but I at least wouldn’t say it if I didn’t mean at least “this post is good in absolute terms and better than most others like it”, and Jacob is claiming that that isn’t actually so. That’s not a nitpick about conventional phatic utterances, it’s an actual disagreement of substance, no?