I just accidentally dragged my profile pic into the post textbox, and apparently that puts a link to my profile there? Interesting. Mastodon is weird.
Works with the profiles of other people on my timeline, too... But why? Someone had to spend time implementing this feature with no use-case... 
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@vaporeon_ i don’t think it’s that mysterious, or mastodon-specific. the user purrofile picture is wrapped in a link to the user’s purrofile; what you are actually grabbing as far as the browser is concerned is that link
@aescling Oh, that should've been obvious in retrospect... I'm such an idiot 
@vaporeon_ that’s just what web browsers do