It would be really nice if the notification told you what part of the comment was considered spam, cause having to go through a long comment to find the exact part the filter doesn't like can be a real pain in the ass.
Not once have I had it look like a URL. It's always been a single word like fun. Seriously, try putting fun in a sentence by itself. You can't, the system thinks that's spam for some reason. And it's not the only one.