I don't recall seeing this in the past, so I'm not sure if this is something new.
On deleted answers, the "Add Comment" link is disabled. That makes sense. But there is also a note saying that comments require 50 reputation with a link to the privileges page.
It seems like either the reputation requirement text or the whole "add comment" section should be removed for these answers.
comments disabled on deleted / locked posts
, but I can vote to un-delete answers - from the screenshot it looks like you don't have that yet. Maybe that's also partially related somehow?