I am pretty sure this is system wide, based on my experience with multiple accounts, but it looks like Twitter has changed who can delete direct messages. In the past either party could delete a message and then it will disappear for both, meaning that there was only one copy of the message. Now only the sender can delete a message. So if you have a lot of people sending you messages, it makes it impossible to remove what one might not want to look at, unless the sender deletes it themselves. The problem is that some people like to keep their messages, PMs, IMs and emails. It is even worst when messages are sent from people that are not following you, so now there is no way to contact the sender to get them to remove it. The results of this are two: 1) The user cannot remove messages; 2) It makes it easy to SPAM people, because they can't remove the messages received.
The solution to this is for Twitter to add two extra columns in their database - a delete column for both the sender and receiver. It will be a boolean column, meaning it can be only true or false. When the system filters which messages to display, whichever column says true for the delete then that user does not get to see that message. The message can be truly deleted when both users have marked it delete either during a routine database maintenance and optimization, or when a user marks a message as deleted the system can check if the other user also has marked it delete. If both have done so then the message can be completely removed, in real time.
Whatever Twitter decides as far how direct messages are managed, it would be nice to be able to delete unwanted ones once again.
BTW, if you are not, you can follow me on Twitter by following either TheTitan or DomainVentory.
So tell me, are you bothered by these changes from Twitter or not?