This question already has an answer here:
Original question was resolved; I'd missed the backtick escapes.
However my second point remains: In comments, unescaped URIs have the scheme stripped off them as part of the process of converting them to links. Thus, a careless attempt to discuss
http://foo.com in comments displays as foo.com.
I don't think stripping the prefix off actually serves any useful purpose. Browsers generally assume the http: scheme and automagically reintroduce it, but other tools generally don't, and not every discussion of URIs is in the context of a browser.
So, low-priority suggestion: Were it my system, I'd get rid of the stripping. It has the potential to cause confusion, and I don't think it has value to offset that.
Concrete suggestion: Rather than displaying as foo.com, display as
Up to you, of course.
EDIT: Yes, I saw the possible dupe. Like the backticks, the answer suggested there is a workaround for the rendering problem... but I still consider the default rendering a problem. It may make sense to combine this question into that one.