One piece of information that would help me to track this down, for anybody who has experienced this issue: does the number of new chats jump up suddenly, or simply not decrement or go up just by 1. For example, lets say you start off with 5 unread chats, and they are all valid unread chats. As you click through them, do you see unread chats go down to 4, then 3, then 2, then at some point BOOM it is back up to 5? Or is it more like 5, then 4, then back up to 5, and it never gets lower than 4 or 5 while you are reading your chats? I hope that makes sense...
More like the latter 2. It will go down by 1, but it quickly starts popping back up. An example might be:
10, (click), 9, (click), 8, 9, (click), 8, (click), 7, (click), 6, (click), 7, 8, (click), 7, (click), 6, (click), 5, (click), 4, 5, (click), 4, (click), 3, (click), 2, 3, 4, 5, (click), 4, (click), 3, (click), 2, (click), 1, (click), none
(click) is where I click the "Game Chat" button to move on to the next chat. After a click it always (or at least nearly always) goes down by 1. But it will seem to get repopulated while I am reading the chat. The sequence above would be a particularly bad episode with 18 clicks to get through the 10 chats plus maybe a couple legit new chats that pop up. Another note is that the number may not ALWAYS go up by one. Obviously, sometimes when it refreshes itself it picks up on more than 1 "new" chat (legit or not).
Final thought ... is there any way that legit new chat somehow reanimates the old chat? I'll have to check whether this has ever occurred where it exclusively cycles through old chat. One of these days when I have 20 or so game chats to read, I'll post a more detailed summary with time stamps.