++ re "(2) I don't think we should be getting in the habit of linkifying existing posts for people; once started down that road where do we stop?" Especially if "quality janitoring" comes to mean "linkifying" every address the poster may have included as text. That could be a very long road.

(NB: as I understand OP, the idea is "linkifying;" NOT "adding relevant links.")

BUT, given that some (many?) OPs are also new to the monastery (as I still am and all were, at some time or another) I'm think the following point (also from (2)): "...if the original author wanted links, he would (or should) have put them there him/herself" slides rather too lightly over the difference between "would" and "should."

"Should," yes! "Would?" ... well, maybe.
But maybe the poster hadn't caught all the niceties of coding a post. "Should?" Yes! But "has" may be a different story.