We create a matrix job, which has one of the axis as such:
"test-124 | -m a,b"
"test-125 | -m w,z"
In the job's shell script we cut the 2nd half and turn it into our parameters for our application.
This fails to create a proper URL for the job.
Full example (note the "-m%20rc,d%20" - this is the issue):
Simple workaround we've used is convert all commas to underscore and later in our script re-set them to commas.