I also found this early discussion helpfull

Solution

Introduce a special format for instance agnostic links (called Lemmy links) that will be opened in the current instance:

for posts: #1@lemmy.world
for users: @ruud@lemmy.world
for communities: [!asklemmy@lemmy.ml](/c/asklemmy@lemmy.ml)

for comments: ~1@lemmy.world

This will open page at https:///post/1, https://lemmy.world/u/ruud, https://lemmy.world/c/asklemmy@lemmy.ml, https://lemmy.world/comment/1 respectively. It will not break existing links functionality as direct HTTP links are still supported.

Bookmark the resource link (or mark this comment as saved on lemmy) for future reference

You didn't type @Magrid@lemm.ee though, you started typing and selected the dropdown box link. This creates a direct link to the user's instance, which isn't great.

If you type /u/username@instance then you will get an instance agnostic link, which will be in the viewer's instance. Eg /u/UnanimousStargazer@feddit.nl - if you click View Source then you will see I did not type a link, yet when you hover over it the URL (for you) is https://lemm.ee/u/UnanimousStargazer@feddit.nl. With an instance agnostic link you stay in your instance and see a federated version of the user's page, which allows you to do things like message them.