The link http://example.com should be expressible in bare markdown as <http://example.com> (omitting the angle brackets is an extension). This is not mentioned on the official documentation. However, it is sometimes useful for disambiguation, e.g. Go to <http://example.com/?weird_=param,>, and do stuff there.
However, the bare version with angle-brackets is not clickable in silverbullet for some reason. It’s rendered with class sb-url (instead of sb-naked-url), so it looks like a link and the mouse cursor changes appropriately, but clicking it does nothing.
Ahhh this clears some things up, I never bothered to look into before. The lezer markdown parser SB uses, by default, has the Autolink extension, which parses these kind of anglebracket autolinks. The node it creates is a URL node inside an Autolink node. SB wants to allow plain urls, so another extension is implemented called NakedURL, which parses, you guessed it, the non angledbracket case. This extension just creates a single NakedURL node.
I was always confused in the code what autolink is, now it makes sense. It doesn’t seem to be handled anywhere really tho, maybe these two cases should just be aligned a little better, so we don’t have the differing syntax tree structure and we don’t have to style both things separately.