Steps to reproduce:

1. Logon to matrix account for chat
2. Pick a group channel name, and right click "Close conversation" or click (X) button

Actual results:

Conversation disappeared, unrecoverable on UI.
Other members in channel receives "user left room" notice
Other matrix app shows channel disappeared (left the room)

Expected results:

A. Moves the conversation to "inactive conversations"
B. Rename to "leave room", with warning dialog to user warning them they will leave the room, and conversation history will be lost

We don't currently have a concept of "inactive conversations" in Thunderbird. We have conversations that aren't currently joined but decided not to support that in the Matrix implementation for now to keep it simpler. However, leaving a room while keeping the TB representation open is unrelated to closing a conversation.

However "closing" a conversation has the same result with all protocols, you leave the conversation and the conversation is removed from the UI. We are aware that this user interface doesn't really match up with other modern chat client semantics and it's something we'd like to address eventually.