To disable the Comments you can go to Administration->Settings->Advanced->CommentsModule->Default Settings and uncheck the Allow Comments checkbox, then restart the application so that the change takes effect. This will disable the comments for all dynamic types along with item types that are not listed under Administration->Settings->Advanced->CommentsModule->CommentableTypes.
If you want to remove the Comments for a specific dynamic type you need to create it in the CommentableTypes section and uncheck its Allow Comments checkbox - see image
I hope this helps.
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