Not sure about this, I did a few grep/zgrep/man in:

/usr/share/man/

and it looks like no space before ( is more common.

man-pages(7) says:

Any reference to another man page should be written with the name in bold, always followed by the section number, formatted in Roman (normal) font, without any separating spaces (e.g., intro(2)). The preferred way to write this in the source file
is:

.BR intro (2)

That's enough justification for me, in general I prefer to have more than a one liner description for all commits.