Hey,
I find this option unusual. I don't think other popular plugins or built-in systems (like :help, :Explore, :Sexplore, :Vexplore) have something like this.

I think the right way for users to customize this is:

• with a mapping
• via command line abbreviation, example cab man Vman (I use this method, although a different abbreviation and it's just for the purpose of being faster, not changing split type)

Well, I like to use the man buffers like the help system, a unique command to reuse the same window. I put all the man buffers on the left with something like autocmd FileType man wincmd H, so that it's similar to NERDTree.
This is something to address two small issues:

• No automatic width alignment, which leads to the wrong formatting (see Reformat text on window resize #14). If I open a manpage with Vman it works as intended.
• With a cabbrev, the history gets littered with the other variants, so you can't easily write :Man and just get a list of the last opened man pages with the up arrow key.

The main issue is really #14, if that's solved then this PR is obsolete since you can just create an autocmd.

And now I really understand

Rebased this into the latest master.

Hi,
as mentioned in the previous comment I'm not the fan of this approach. In fact it's the first time I see it.
I'll let other users upvote this feature and if ppl like it then we'll merge.

Very well, no problem.

I just rebased this (and will probably continue to do so) to keep my branch updated, since I use it in my configuration. Don't take it as some kind of pressure to merge it.

I think this aproach is not uncommon. I use some plugins that do it like this. Bexec and CtrlP for example.
+1 from me.

(Not to forget the g:manpageview_winopen option in Dr. Chip's manpageview plugin)

I agree with @lucc E.g., vim-tldr offers a similar option.

See: https://github.com/wlemuel/vim-tldr