I thought I'd pass along some info which would be very helpful in organizing runs and other gatherings. I posted this question in the Support forum.
Ability to edit post
In addition to what's in the thread, I also got other tips via PM.
Bottom line, when organizing a run we can request a mod (by PM or by reporting the post) to allow indefinite updates to a single post, specifically the first post in the thread, for the purpose of updating it with the latest event information. That way the organizer can keep the first post up to date and anyone can just go to the first post to get all the necessary info instead of having to read the entire thread to get it.