As stated at the bottom of this page :
I would assume this also applies to comments.
The attribution part is what I think gets infinged upon when a comment is edited.
Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
When a comment is edited by an user different than the original poster there is an small icon for it. And a tooltip pops up with the number of editions.
But no mention that this is not the text by the original author is made.
Is this usage of the user posted comment in agreement with CC BY-SA 3.0? Are there other stipulations besides CC BY-SA 3.0 that apply?