Sandbox example: https://meta.stackexchange.com/a/328811/192262
I can type http://[::1] in a question or answer, and it'll automatically turn into a link. I can also use markdown to format it as link, if I wish to give it a custom text.
In comments, however, neither works: it's not autodetected, and
[http://[::1]](http://[::1]) also does not turn into a link.
I'm not sure why the markdown/hyperlink parser handles the two cases differently, but as far as I know, there should not be a difference. Seems like a bug?