I can tell you what happens on MacOS-X.

> 1. press option key

A 'flags-changed' event.  The flags reflect that option is now  
pressed.  The raw key-code is also set in the event-object.

> 2. press e key

Key-Down.  You get the raw key-code, the 'e' string and flags that  
tell you that the option key happens to be down.  The repeat flag is  
0.

> 3. release e key

Key-Up.  Other data same as above.

> 4. release option key

Another flags-changed event, telling you that the option key is no  
longer pressed (also with the raw keyboard code).

> 5. press e key again

Key Down.  The flags tell you that no modifier keys have been pressed.

> 6. release e key

See above.