You can see it in this issue:
This comment was added by the issue reporter (KS in this thread), but is attributed to the repository owner.
The list of allowed actions for this comment includes editing, which suggests that the bug goes deeper than just a name mix-up and actually switches the user behind the scenes, which is unrecoverable loss of information.
It appears to relate to assigning issue to the user that becomes the comment author. Here’s another example:
The comment was added by the issue reporter, but it is also attributed to the repository owner.
Can somebody please look into this? I hope you can recover original comment authors, as it is quite hard to follow who commented what now.