SVcrossDOWhy people say good morning (or something like that) on chat after a night?
Th4tGuyIIIf you're talking within the same day, I would consider it fine to continue talking.
...But if you're talking overnight or longer, I feel like you need a greeting of some kind to acknowledge that the time has passed. I wouldn't call it rude not to, but it's an extra pleasantry.
The time seems to be different according to the relationship.
As others have said, I think that comes down to how people view online conversations.
I personally view them as an extension of in-person conversations, so a lot of the same mannerisms carry over for me.