It would be great if we were able to use the "Add to Comment" function as this is heavily used by our organization for administration actions.
I am looking into this issue.
I have updated the New-PWDocumentComment to fix a bug in the code. I have also added the ability to accept ProjectWise document objects via the pipeline. Take a look at the help. Get-Help New-PWDocumentComment -Full
This will available in a future release of the PWPS_DAB module.