your list is currently a single value. You need to put the comma separated values in their own double quotes (e.g. ["v1","v2"] instead of ["v1,v2"])
What is the current limit?
100 values per list. Total number of list columns depends on the size you set for the column model similar to string columns.
I think there's a cumulative 1000 character limit for all values in a single list as well