Editing man pages in vim is not exactly my favourite task. There are two reasons: the syntax of man pages and the need to frequently check the page with man after few edits. However, I have to do it often for Buku and google-cli. Seems like those days are over, thanks to the new web-based utility Grapse.
Grapse makes man page authoring as simple as it should be with a side-by side live preview pane. There are no other settings at the moment and I would think a useful service like this need not be bloated with feel-good features.
Grapse is open source and can be deployed easily on your system. However, I prefer the hosted counterpart.
If you are the maintainer of a Linux utility with a man page you would feel lucky too!
Usability: Depends on how well you know man page syntax