(a) Version 0.4.10 segfaults when I try to run it (PPC Mac / OS 10.5.8). I'll go insert some debug writes and try to pin down where it happens later.
(b) All versions from 0.4.5 through 0.4.9: using "--charset", I can post Greek text to Blurty, Deadjournal, Insanejournal, Journalfen, and Scribbld, but NOT to Livejournal or Dreamwidth.
I created a file, test.tmp, containing the text "Αγνοήστε αυτό το πείραμα" (which Google Translate says means "ignore this experiment") and then tried to post it using Clive with the following command:
clive -u dglenn -w {mypassword} -s test --charset utf-8 < test.tmp
(For 0.4.5 I used hacked versions with other sitenames substituted for "livejournal.com" in the source. For 0.4.6 through 0.4.9 I changed the site via .cliverc.)
On Blurty, Insanejournal, Deadjournal, Journalfen, and Scribbld, this had the desired/expected effect: a journal entry in Greek text. On both Livejournal and Dreamwidth, I got "An unknown error was encountered while posting your message".
Pasting the same text into the Post Entry form at http://www.dreamwidth.org/update worked just fine -- I got the Greek text in a DW entry.