Good question!

For me, personally, I like to share posts with my friends who are non-Lemmy users. I want to share the same domain with them every time so they start to get used to it and don’t have to wonder what this random site I sent them is.

Plus, I trust that lemmy.world will be fairly stable, so I shouldn’t have to worry too much about them getting an error when they try to open it.

Sure! For me it would be ideal to have something analogous to the webUI where all posts and comments point to the same domain. Also this is important for security, since individual users might trust their own instance more than others, and any instance can go rogue and serve malicious scripts.