We use the 2.0 Jira Plugin to add comments to Jiras. We have the problem that every such request causes a Thread Leak - see the "diff" output of "jstack" below.
Seems that this is caused by using JiraSite.createSession instead of getSession() in Updater class. Changing it to getSession worked for me.
Mind that I havent yet tested for the "// TODO: we should check for session timeout, too" in JiraSite.
Output of the thread-list diff - we can see many additional "httpclient-" threads