If you post a chat message like [tag:foo]http://example.com/ (note the lack of a space in between), it will be converted to:
Now when you view the same message in the chat transcript it looks like this:
It's failing to convert to a link. However, if you did put a space it between, it works for both. There shouldn't be a difference in how this markdown is processed in the chatroom and the transcript.
Also, yes I know the lack of space is stupid on the part of the poster, but the rendering should be consistent. I expect when a link properly renders in chatroom it would do so in the transcript.
