I did do some testing with this. When I load Target, an empty value is
sent as a user.categoryId so that's why you'll see it as an entry. Here
are the steps for a quick test. 1. Load the homepage with the mboxtrace
parameters in an incognito window.2. Push an event including the
user.categoryId parameter with multiple, comma-separated values to Adobe
Target using the console--see code below. adobe.target.trackEvent({
"mbox": "target-global-mbox", "params": { "user.categoryId":
"one,two,three,fou...