Today I commented on an answer to How should I deal with a player who wants to dictate loot distribution?, asking the answerer for clarification (and implicitly suggesting an improvement at the same time).
A few more responses were posted after mine, including a direct reply to mine. As I was typing up a second comment (which I've since deleted, as it makes no sense now), the additional responses, including my request for clarification from the author, were all deleted.
My comment to OP was not addressed by them via reply or edit to the answer (and likely not even seen by OP, given that only survived for such a short time), so it certainly didn't fall under the 'obsolete/no longer needed' reason.
Why? The comment box description says:
Use comments to ask for more information or suggest improvements.
This is what my comment was doing, to the best of my knowledge.