Random comment coming from Discord: 
1. https://www.openstreetmap.org/way/616764563 should be `lanes:backward=2` + `turn:lanes:backward=through|right`, correct? 
2. `change:lanes:backward=not_left|yes` can be added to indicate this
On related challenges, painted median is already easier to handle than long ghost island merges for both lane merges and 1 lane gain.