Hi Tim,
Assuming you are using 2.0 version,
There is a Cmdlet that gives access to some of the execution time variables and you can use that in your custom command that is part of your workflow:
Get-WfaRestParameter("workflowName")
Get-WfaRestParameter("jobId")
Get-WfaRestParameter("userName")
Please take a look at the command code in the certified command "Sent email" to see its usage further.
Execution comment is currently not available in this.
Thanks,
Shailaja