The problem is that you're sending the complete text from the textbox as a filter (e.g. "Name1, a") instead of just the part after the comma (e.g. "a"). You're correctly making requests (as can be seen by looking at the Network tab in the developer toolbar of your browser of choice), but you're not sending the correct data as part of the query. It seems as though you have started with a copy of the code from http://jqueryui.com/autocomplete/#multiple, but you haven't used the extractLast method. If you change the data part of the json call from
data: {
filter: request.term,
pagesize: 10
},
to
data: {
filter: extractLast(request.term),
pagesize: 10
},
It should work. I have updated your jsfiddle (http://jsfiddle.net/85SAF/10/) with this and it seems to work fine.
Hope it helps!