Emanuel Berg <moasenwood@zoho.eu> writes:

[...]
>
> It is just amazing how this has been handled,
> to care so much for the IRC client and also to
> be able to strengthen the reasons for the
> policy by finding one RFC!
>

:-) Thanks, Emanuel.

>
[...]
> Here I wonder why does the erc-button has this?
> Don't Gnus, Emacs-w3m, man mode, virtually every
> mode that is about communicating have
> a tendency to come across hyperlinks?
>

Historical reasons, I’d imagine?

Doing a git-blame, it seems that ‘browse-url-button-regexp’ was
introduced in a32e1feb438e793a8378671c7124d226b58f65f0 [0], where Lars
refactored ‘gnus-button-url-regexp’ out from “lisp/gnus/gnus-art.el”
over to ‘browse-url-button-regexp’ in “lisp/net/browse-url.el”,
presumably for the very reason of other packages being able to use it
for controlling what’s considered a button.

[0]: https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=a32e1feb438e793a8378671c7124d226b58f65f0