Idle observation: I haven't seen any obviously ~viral content~ on Mastodon. Metadata (i.e. shares and favs) is not obvious - not being displayed on the main feed, only on single post view.
I'm not sure if this is an intentional design choice to avoid cognitive biases with viral posts, if other system designs are affecting it, or the community is simply too small and compartmented to have post virility like we've seen on other sites.