It appears that the plugin does not correctly replace environment variables when it sends out "started" messages.  For example, ${COMMIT_BRANCH} is not resolved for the started message, but it is on success:

Feature Branch Build - #1095 Started by changes from Daniel Kirkdorffer (6 file(s) changed) (Open)
Branch: ${COMMIT_BRANCH}

Feature Branch Build - #1095 Success after 2 min 34 sec (Open)
No Tests found.
Branch: EPC-648_Ordering_Filters

This seems like a bug to me.  I can't see why the plugin wouldn't know the COMMIT_BRANCH when it sends out the "started" message.

We are using version 2.2 of the plugin against Jenkins 2.32.2.