When submitting a video I often have to pause for some time to check out in which channels this video could belong. This usually means going to their respective subdomains and reading the posting criteria.

My tip to make this process easier would be to make the channel text beside each checkbox a link to that subdomain (or a specific page with posting guidelines for that channel)
This might also have the added advantage of less videos posted to wrong channels.
Alternately the information you get when you hover over the channel text could contain more relevant information.