Thanks, Maxim, for implementing some of my suggestions in commit 
06dc36ffb7cde821a4762b299d1c95b3788ba110, as I coincidentally 
found out when reading the commit log.

By the way, I still believe it's less off-putting for average people to see 
two lines of regular expressions instead of 28 lines of symbolic 
expressions.

I'd now like to make another suggestion, appended as patch, that allows for URLs like https://issues.guix.gnu.org/12345 to be opened in debbugs-mode within Emacs.