When a larger discussion happens in comments, the participants are invited to continue that discussion in chat, instead of in the comments. This creates an automatic comment "let us continue this discussion in chat" linking to the chat room created for that discussion.
Now, if the discussion isn't long enough the room is automatically deleted, breaking the link in the automatic comment for non-mods.
I suggest that either:
- The comment containing the link is removed entirely
- The deletion criteria for those chat rooms are relaxed
A recent case where the comment link was broken can be found on Math meta (in this case there are 8 posts in the chat).