Celeste is in theory capable of sharing the same mail database between
two different Celeste windows.  It is in fact a somewhat complicated
thing to coordinate, and as far as I know nobody uses Celeste this way. 
This can however be revisited if there is popular demand.

I also agree with you that the inconsistancy notification was too
obtrusive on the (infrequent) times that I have seen it.  I will improve
that.

Mike