Moderators have access to a tool that allows the deletion or relocation of multiple chat messages. This can be very useful to clean up some less constructive or outright offensive exchanges in chat.
But if you actually use the tool you'll quickly notice that the relocation tool is far superior to the deletion tool. If you delete a larger number of messages, the chat will look roughly like this:
(removed) (removed) (removed) (removed) (removed) (removed) (removed) (removed) (removed) (removed) (removed)
Each removed message is deleted individually, and all those empty messages are visible in the live chat and for moderators and room owners in the transcript as well.
Now, if you're a moderator and come in late to the whole situation, it gets very tedious to find out what the heck happened to warrant mass deletion of those messages. The only way to look at a larger number of removed messages in chat and keep your sanity is to use a user script that loads them automatically, otherwise it's three clicks per message and you can only view them one at a time.
Compare that to the relocation tool, where chat looks like this after you used it:
→ 10 messages moved to Trashcan
All the moved messages are removed entirely from the chat room, and a single message is left that links to the new location of the moved messages. This is far more tidy than the result of deleting multiple messages.
Now, if you know all this you can use the relocation tool as an improved deletion tool. It leaves less of a mess in the original chat room, and if the target room is private, it's as good as deletion as only moderators can see private rooms. However, a major disadvantage to a private trash room for this purpose is that only moderators of the parent site of that room can see inside, which can be problematic for other mods or room owners trying to reconstruct what happened. So the trash room must be a chat room without a parent site to allow all mods access, but this still doesn't allow room owners access.
So what I propose is to reimplement the remove tool in a way that works like the relocate tool, or maybe even directly as a relocation to a private chat. There would be a predefined trash room (or multiple, not sure how this would work for simultaneous deletions in multiple rooms) that deleted messages are moved into automatically. This would lead to a cleaner transcript, and a much easier way to figure out what is in those deleted messages, if you need to.