No duplicated messages

I have restricted the number of messages each user may send to others in a given time. This is to avoid mass spammers sending hundreds of messages before I can stop them. I have set up to a maximum of 5 messages in any given 5 minutes time span. I’ve noticed some users may send legitimate messages more often than that sometimes, but I’ll wait to see if they complain about the new limitation.
I have also blocked messages from being sent multiple times, as when you click twice on the ‘send’ button. It was quite annoying to see the same message repeated twice or three times in your list of messages.