xat search allows you to search for what people are chatting about. xat.com/search
Here are some more details about how it works.
Private messages, private chats, and messages sent in rankpool are not searchable.
If you set your chat to "don't list...", "don't store messages... " OR "members only..." messages are not searched.
Messages up to 8 hours old are searchable.
Currently you search in messages, you cannot search for names or IDs.
You can use advanced search queries, example:
xat AND chat
will only show messages that contain both "xat" and "chat" in them.
You can also do:
(football AND (fun OR boring)) OR (baseball (exciting OR uneventful))
This will display messages like "football is fun" or "baseball is exciting". It will NOT include results with "football is exciting".
How to opt out?
If you do not want your chat to be on xat.com/search anymore, you may click "Edit Your Chat" (above Sign out), then "Extra features". Scroll down and check "Don't include this chat box on any lists or charts". This will remove your chatroom's messages from being searched. Note this will also remove you from xat.com/groups, promoting etc. You may undo this at any time.
This is on a chat-by-chat basis so you might want to ask the owners if search is removed (or try to search for messages yourself) if you're cautious. There's no way to block your account from showing up.