Commercial spam seems unlikely, but it's certainly low quality content. We already know federation works, this is the equivalent of the "this is Bob, copy and paste Bob to all your friends' profiles" comment from the 2000s.
All the links are directed to social.heise.de, so it's definitely got spammy characteristics imo, even if it's not commercial spam. While awareness raising about federation functionality is probably fine, it's also presumably meant to direct traffic to that specific instance, which is arguably a form of advertising.
That's just how Mastodon tags work, they get turned into HTML <a> tag with the href pointing to the local instance's view of that tag. Lemmy then turns that HTML into markdown, hence all the links to poster's instance.