Keep an author's last event description in case another author mistakenly overwrites it.
Maintain a table of description edits with columns event, author, description, timestamp. Populate the table with all existing event descriptions with a default author (admin or 0-id). When a user writes a new entry to the table, update/insert the event-author entry. Use that table to recover a version if necessary.
Event editing is setup to allow a participant the ability to edit events at one venue. Let's extend that logic to listing RSVP details and the organizer column.