GoDoc automatically linkifies RFC references such as "RFC 5301", "RFC 5301 section 1", "RFC 5301 page 10", and so on.
gddo does not.
Yes, this was part of the change to use the new doc comment syntax, which supports links. I thought that it might be better to encourage users to use the new link syntax instead of hardcoding heuristics for RFC links into gddo. What do you think?