Comments are not currently supported by RadSpreadsheet, but they are already in our backlog. I have created item in the Ideas & Feedback Portal
. I suggest you to follow it. This way you would be notified about the progress we make on the feature.
Let me know if I can help you with anything else.
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.