if all they have to say that's nice about the post is a stock phrase that could be equally well applied to any original text, I'd prefer they skip it.

What I find interesting about this is that you're basically saying that their signal isn't costly enough to make you feel good.

This is something that seems to apply more generally when complimenting. Direct praise seems cheap, at best a signal of supplication. It is often better to identify something that the person does and express approval of that activity in general, and hence compliment their identity.