The only issues I've heard of are when someone uses their addresses for casino games or sports betting.
Sending funds from exchanges to other exchanges or casinos is not recommanded because the latter or most of them will generate deposting addresses that have an expiry date and exchanges do not process withdrawal requests instantally.
When it comes to delaying transfers, they do so for security reasons. They are simply afraid of being accused of money laundering. It is possible that they do it too carefully.
Maybe. But this is not an excuse to not responding to their customers open support tickets.