In an earlier version of the plugin parameters could be used in custom build messages. Now they are not processed any more.

To configure custom build messages: job > configure > Gerrit Trigger > Advanced > Custom Build Messages
Use a parameter like <CHANGE> in one of the messages (like Build Successful Message).
The expected result is that the parameter is replaced with it's value, instead it is not processed and it is output as is.

Similar functionality can be seen in the server configuration: Jenkins > Manage Jenkins > Gerrit Trigger > Edit server > Advanced > Gerrit Verified Commands