So, old installations have plenty of those, and and I don't see any reasons they shouldn't be migrated too to internal links where such options exist, and to new URLs in all cases.
External links are migrated as best as possible. This is done as per #6389. Not all can be migrated though, but will be adding more migration with the changes made for this ticket. The changes made for this ticket will be to match exactly how Joomla handles the com_content component.
At some point we need to get completely rid of task=...
It's already gone and has been since CB 2.0. The only trace of task left is converting it to view when it's supplied for B/C. Old installs that never updated their menu items are strictly the problem here. Joomla does not parse external menu items when SEF is enabled.
Sorry guys, just found out that I can apparently edit anything on the forge.... Just wanted to try it out and it worked...
Edit is how you add comments. It's not user friendly here, but it's not really intended to be as it's just our issue tracker. You do not have permissions to edit the actual ticket though or at least shouldn't.