As far as I can tell, there is no point to flagging comments as "obsolete". The moderators will just decline the flags.
A scenario:
- Answer is posted in comment #1.
- Original poster asks (in comment #2) for a clarification of comment #1.
- Follow-up comment #3 clarifies comment #1.
- Original postersposter asks (in comment #4) that comments #1 and #3 be written up as an answer.
- Comments #1 and #3 are written up as an answer.
- The original poster accepts the answer.
- Two years pass.
- In a meta-thread, moderators encourage flagging obsolete comments.
- Comments #1, #3, and #4 are flagged as obsolete -- because they have been incorporated into an answer.
- The flags are declined.
Conclusions:
- Flagging obsolete comments does no good, even when the obsolescence is obvious.
- If the moderators disagree with conclusion #1, the moderators will need to change how they handle "obsolete" flags.