@grumpygamer I'm sorry if I misunderstand what you mean but I think I can:
if I go to https://mastodon.de/@grumpygamer@mastodon.gamedev.place/113189402225733317, I see your post on my instance (mastodon.de) being logged in.
if I go to https://mastodon.gamedev.place/@grumpygamer/113189402043320068, I see it on your instance where I'm not logged in
still I agree with you that the UI should by default link to the former, not the latter.
I hate that you can't link to a Mastodon post without it taking you a different server. It's nuts that those links aren't swizzed on the sever. Always taking me to a different server that I'm not logged into is the Achilles heal of Mastodon. Non-tech users are completely confused by this. It's not their fault, it's Mastodon's fault. I know it's not easy to fix, but if Mastodon wanted to fix one thing keep new users, this is it.