The global inbox accounts for basically two kinds of messages:
- Site responses like answers and comments. These get added pretty much instantly at the time of the event.
- Chat messages in recent rooms. These are delayed by 15-23 minutes, during which any additional messages will be added into the same notice.
Since chat messages can come in high volume, it makes sense to have the delay and aggregation of messages - a lot can be said to you in the span of 20 minutes. What's really confusing, though, is that even though it will be put in your inbox 20 minutes late, its position will be the time stamp of the original message (which is how I derived the 15-23 minute figure).
As a result, any site responses you get within those 20 minutes (an oft occuring scenario) will still be at the top of your global inbox. The chat responses will be buried somewhere lower, with no indication of them being new. If you've been absent a while, it can be especially confusing in how it might populate it when you're mentioned in multiple 20 minute segments.
I'd like to request that the global inbox be arranged in accordance to when the entries are added, rather than according to the timestamp of the first chat message. This way, when you get notice of a new event, whether it's a site response or a chat message, you can immediately find out what it is.