I guess I haven't seen the crit in question here. I have seen some concrit at smutmas and it's all been about the mechanics of the story that doesn't relate (or should't relate) to the request. For example... there was a piece of concrit about a timeline in the story being confusing. That's a mechanics issue that relates to the author. I don't see anyone saying "hey, give me a confusing timeline".

I would never comment on something that could be construed as part of a request (ie, the bottom!harry comment in discussion). We all have our preferences and I would assume that that was a request.

I'm thinking I'm probably splitting hairs here but basically what I mean is things that could be construed as part of the request (scenario, pairing, top/bottom, etc), I wouldn't comment on. Mechanics of the story (phrasing, awkward dialogue, plot holes, etc), I would.