It seems to be a shortcut to open the comment url. Specifically opens the full article but at the height of the comment from which the link was generated, by pressing the icon.
There is a bug and the links are not being generated correctly, because they lack the part of the url that refers to the publication in which the comment has been made.
I will now make a comment to have a practical example.
I don't think this is a bug. The point of this button is not to generate a link to be opened in a browser, but rather one to be copy-pasted in the searchbar of any fediverse instance.
I can use it for example if I see your comment by browsing directly on lemmy but want to answer it with this Friendica account.
In fact, the link to generate the page you are talking about can be obtained by clicking the "chain link" icon next to it
Yes, thanks. Anyway I've seen that and I mentioned it.