/usr/share/man/man8/mkfs.reiserfs.8.gz is in reiserfsprogs 1:3.6.24-3.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man8/mkreiserfs.8.gz
/usr/share/man/man8/mkreiserfs.8.gz