Hi, can you please have a look at this issue and see if it's a bug that needs fixing?
https://knowledge.safe.com/questions/42262/to-use-comma-in-variable-of-workspacerunner.html
My colleague stumbled into the exact same issue last week. We had to work around it by substituting the comma for something else, then using a StringReplacer in the child workspace to restore the value.