This is an artifact of having very large forums. With such a large number of people commenting on the same posts, people start making bids for attention, rather than actually commenting on the OP. Stuff that gets the most attention, rather than furthers discussion floats to the top, and people then comment on that in order to be seen.
This behaviour then filters down to smaller spaces.
If you don't want this kind of thing to happen here, participate in smaller communities. Resist the pull of community centralization.
brownpaperbag
Nepenthe