Yes, this is it. When a post 'blows up' like this and gets linked to from a bunch of outside sources, it creates a big spike in the volume of comments in the mo

Yes, this is it. When a post 'blows up' like this and gets linked to from a bunch of outside sources, it creates a big spike in the volume of comments in the moderation queue---i.e., more work for the (unpaid) mod team. If these comments are all tangential to the subreddit's purpose (here, identifying unknown objects), it can be much easier just to lock the thread.