I tried to link in a comment to this image:
However, it gets cut off semingly at a pair of underscores surrounded by a similar pair of non-alphanumeric characters:
and is displayed with the remainder in italics, except for the surrounding underscores:
<a href="https://upload.wikimedia.org/wikipedia/commons/8/85/Concorde_Cockpit_-" rel="nofollow">upload.wikimedia.org/wikipedia/commons/8/85/Concorde_Cockpit_-</a><i>geograph.org.uk</i>-_1357498.jpg
This answer by Jeff Atwood from back in 2009 is on the only question I can find easily that isn't closed as a duplicate, but it says that underscores are escaped. This isn't (URI entity) escaping, it's rewriting, and it's breaking perfectly legitimate links, for example in the comments to this answer on Aviation SE.