This (or similar) problem was mentioned in JRA-122.

Non-ASCII characters are entered correcty into the database, but are displayed as questionmarks ('?').

Encoding is set in JIRA perferences as UTF-8. HTTP responses from the server are correctly marked as "Content-Type text/html;charset=UTF-8".

I added <input-charset> elements to weblogic.xml, but it didn't help.

I must emphasise that input is not mangled by WebLogic (as it is correctly written by JIRA into the database). It seems that the only problem lies somewhere in the rendering phase.