I note that is now says in the wiki to not use the url key. Unfortunately, I have used this on a few occasions in the past. Nodes with this key are now inaccessible: in Potlatch and on the main map they don’t show up at all, in JOSM they show up as buttons, which open up the link, but I can’t select the nodes in any way, not even by drawing a box around them.
Actually, I made a mistake here: the web link button is not part of OSM, rather it is the Links field from waypoints in an attached GPX file. The only problem that remains in JOSM now is that the name of the waypoint is not displayed when the Links field contains something. I guess I should file a bug report.