how to disable / circumvent it
Currently, there is no way to do so. This has been requested on MSO many times. Not sure if the limit will be removed, but there might be some changes.
As soon as you submit your comment, the time limit is controlled server side. So, again, no way to circumvent it.
also the behavior of hitting enter key is w** a bit ...
Poof! They are gone.
On a serious note, that is normal behavior. Those questions were tagged with ida before the synonym relation to idapro was made. Tag synonyms affect future associations, whereas past tagging needs to be handled explicitly/manually. I just did the retags.
What is the time-zone that is used for determining when the day begins
can something be done to cater for different time-zones?
This has been suggested before on Meta Stack Overflow and has been status-declined