Hello,
my language (Czech) use letters with diacritic ("ěščřžýáíé ...").
In utf-8 strlen('ě') == 2.
Problem:
upper limit is "6"
comment box contains "abcědef"
result would be "abcěde"
but in real is "abcěd"
Solution:
in function comment_trimmer add before 1st line
$length += (strlen($totrim) - mb_strlen($totrim, get_option('blog_charset')));
Michal
http://wordpress.org/extend/plugins/gregs-comment-length-limiter/