[Theme: TwentyEleven] Remove 'posted on/at' from comments

A couple of days ago I removed the ‘posted on’ date and time from under the title on all blog posts.
Now I notice that when someone comments, it says “(commenter’s name) on at said“, but with no date or time.
How do I remove that, please?
You can see what I mean in the comments here http://www.topfloortreasures.com/found-poem-freebie/