Requiring “effort” (independent of quality) is a proof-of-work scheme meant to tax criticism.
Proof-of-work was originally invented to fight email spam. The analogous argument plausibly applies here: evaluating quality (e.g., letting a human read the email to decide what to do with it, trying to figure out whether a criticism actually makes sense) is costly, so it’s more efficient to first filter using a cheaper-to-evaluate signal/proxy like work/effort. (I don’t think this is the OP’s argument though, which is based more on low effort criticism feeling unpleasant or discouraging to some post authors. I’m kind of going off on a tangent based on your mention of “proof of work”.)
Proof-of-work was originally invented to fight email spam. The analogous argument plausibly applies here: evaluating quality (e.g., letting a human read the email to decide what to do with it, trying to figure out whether a criticism actually makes sense) is costly, so it’s more efficient to first filter using a cheaper-to-evaluate signal/proxy like work/effort. (I don’t think this is the OP’s argument though, which is based more on low effort criticism feeling unpleasant or discouraging to some post authors. I’m kind of going off on a tangent based on your mention of “proof of work”.)
ETA: I recalled that I actually wrote a post about this: Think Before You Speak (And Signal It).