The order of caret movement and text insertion/deletion events for gnome-terminal differs from all other gtk text widgets. The normal event orderings are the following:

Insertion
1) insert
2) move

Deletion
1) delete (delete key)
or
1) delete (backspace key)
2) move

In the current version of gnome-terminal, the event ordering is the following:

Insertion
1) move (to the location one past the last character in the text to be inserted)
2) delete (all text to be inserted before it's inserted)
3) insert (the text to be inserted)

Deletion
1) delete (delete key)
2) insert
or
1) move
2) delete (backspace key)
3) insert
 
The fact that insert AND delete events are always fired whether text was actually inserted or deleted is confusing for ATs. Furthermore, putting the move event before the insertion/deletion makes it difficult for an AT to determine whether the movement was due to text insertion/deletion or navigation without insertion/deletion. 

The problem is that the AT has to "predict" whether an insert/delete will follow a move before it can tell the user what has actually happened. This requires hacks like knowing what key has been pressed to cause the event (which discounts programmatic movement, insertion, deletion, mouse clicks, etc.) The standard gtk event ordering mitigates this problem by first letting the AT know what is causing the movement.