Submissions put in the second-chance pool briefly appear (sometimes "again") on the frontpage, and the conversation timestamps are reset so it appears like they were written after the second-chance submission, not before.
I suppose they want to make the comments seem "fresh" but it's a deliberate misrepresentation. You could probably even contrive a situation where it could be damaging, e.g. somebody says something before some relevant incident, but the website claims they said it afterwards.
I think the reason is much simpler than that. Resetting the timestamp lets them easily resurface things on the frontpage, because the current time - posting time delta becomes a lot smaller, so it's again ranked higher. And avoiding adding a special case, lets the rest of the codebase work exactly like it was before, basically just need to add a "set submission time to now" function and you get the rest for free.
But, I'm just guessing here based on my own refactoring experience through the years, may be a completely different reason, or even by mistake? Who knows? :)
There is some action that moderators can take that throws one of yesterday's articles back on the front page and when that happens all the comments have the same timestamp.
What do you mean?