Partial screenshot of Special:Preferences#preftab-5 (Watchlist) with garbled subsection.
Use full screen with, or full line width, respectively,
for the "Display options" subsection in Special:Preferences#preftab-5 (Watchlist)
Attached sceen shots show that the subsection layout looks pretty garbled,
and that there is plenty of space which can be used to make it look better,
even with a rather small screen width.