There is a little problem with the BBcode plugin, when using the QUOTE tags. The text that is quoted appears in the comment with the title QUOTE. But QUOTE is an English word and is hard-coded in the "serendipity_event_bbcode.php" script (lines 207 & 208).
It would be better to have it in a variable in the language files.
PS: And to have the possibility to add new bbcodes would be the paradise!