`Man` uses `groff`, which is accepting only ascii as input - for example UTF-8 characters are not displayed correctly. Current version of `groff` is 1.19.2, which doesn't support -k, -K and -D flags. Those flags are supported by `groff` version 1.22.3 located in ports. Flags mentioned use `preconv` to escape characters from the outside of ascii. `Preconv` is already present in the FreeBSD.

How-To-Repeat:
1. create man page inside localized man directory MANPATH/pl.UTF-8/man1/manproblem.1.gz with polish letters (ęóąśłżźćń)
2. Properly setup locale, fonts, keyboardmapping, etc.
export LANG=pl_PL.UTF-8
3. Show man page:
man manproblem

Proposed solutions:

1. Use newer version of `groff` and update `man` script (-D flag says to use `preconv` as preprocessor to `groff` as well as specifies input encoding - this was already proposed option in linked bug issue):

333c333
<               NROFF="$NROFF -D$nroff_dev -T$nroff_dev"
---
>               NROFF="$NROFF -T$nroff_dev"

2. Use `preconv` as preprocessor and update `man` script (doesn't require to use port version of `groff`):

333c333
<               NROFF="$NROFF -T$nroff_dev"
---
>               NROFF="$PRECONV -D$nroff_dev | $NROFF -T$nroff_dev"

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> PRECONV=preconv