If the comment flagger is not visible to moderators, could an exception be made by way of an indicator for the specific case of the "obsolete" comment flag being raised by the comment's addressee.
For example, consider a comment such as:
@someuser thanks for the feedback. I've modified by answer accordingly
I normally allow a TTL of about a day for this kind of comment - it's clearly not that important in the long term, but it seems fair enough to allow some dialogue between users as they refine their answers.
Now consider it is then flagged by @someuser as "obsolete". This situation clearly means the comment's usefulness is ended and it should be deleted. But if the time since posting the comment is small, without the knowledge that the addressee has read it, I would tend to wait a day or so to allow time for @someuser to read it.
I propose that if the addressee flags this comment as "obsolete", there be some kind of indicator visible in the flag queue, so the moderator reviewing the flag can confidently delete it asap after posting+flagging (sure, some/most mods may just delete it anyway).