![](https://media.kbin.social/media/e5/59/e559ede17c57b24aa1e96b6b4b900849e85a37fc6f5d82cb8249e6b5b6778857.png)
![](https://lemmy.world/pictrs/image/eb9cfeb5-4eb5-4b1b-a75c-8d9e04c3f856.png)
Lemmy (and Kbin for that matter) very much do the same thing for posts. I don’t think they fetch URL previews for links in comments, but that doesn’t matter: posts and comments are both fairly likely to end up spreading to Mastodon/etc anyway, so even comments will trigger this cascade.
Direct example: If you go to mastodon.social, stick @fediverse@lemmy.world
in the search box at the topleft and click for the profile, you can end up browsing a large Mastodon server’s view of this community, and your very link has a preview. (Unfortunately, links to federated communities just result in a redirect, so you have to navigate through Mastodon’s UI.)
View -> User Interface, change to Tabbed or Tabbed Compact (or Notebookbar in old versions).