As far as I can tell, comment shortcuts have been around since basically forever.
The [tour] link got added sometime soon before June 6, 2014 (officially confirmed on June 11†), a short while after our About page instead became a Tour, and references to it got renamed accordingly over the next few months. Before then, however, we used [about] to ...
The comment formatting section of the editing help pages lists all the available shortcut links you can use in comments, including [help] for the help center. As of posting that is:
[meta] – link to the current site's Meta; link text is the site name
(e.g. "Super User Meta"). Does nothing if the site doesn't have (or
already is) a Meta site.
Magic links are hardcoded into the site software itself and as a result are network-wide, not per-site, so although technically possible in theory, the likelihood that Staff would add a magic link to every SE in the network that leads to RPG.se's meta about RPG forum alternatives is unsurprisingly very low. ;)
Although, as SSD explained, network-wide changes for an RPG.SE-specific code won't happen, there's still a labour-saving work-around available: add a premade comment with the forums link to the auto-comment script.