I certainly dont know the full story behind the strip, but could be justified as the arm WAS ripped off by an Ogre and regenerate (or insert other healing spell here if not RAW D&D) was used later.
My guess would be a bug in connect for users coming from different instances.
Most likely, @Metriximor@lemmy.world was taken to https://lemmy.world/post/837105 instead of
https://ttrpg.network/post/837105 ...
If that's the case then that would a bug in how the Connect app deals with absolute vs relative URLs and not something you can fix on your end.
For linking to communities, we can use this format which should work fine regardless of which instance you're coming from !rpgmemes@ttrpg.network
I do not know of a similar way for linking to posts.