If you use the "Edit Posts" menu, you'll have a list of all posts with comments. If you click on the appropriate "comment" link, you'll be temporarily put into single post mode, with the comments displayed below the post - and there will be a trash can available for each comment. If you find this inconvenient, you can permanently change the Comment Form Placement option, to show comments either as "Full page" or "Embedded below post".
(Update 10/28 12:00): Blogger Support is aware of the problem.
We'll keep working on this one. ... I'll check into this ASAP.