Although it won't become apparent until Thursday, I've just pushed an update to the trade system where you can send a private message at the same time you send a trade offer or reject a trade. This has been pushed to MFN-1 only at this point in case this update caused any issues with the website interface (I had to do a few things to the javascript that has the potential to break something, so I'm rolling out the update here first before I push it to the other leagues).
Let me know if you see anything odd as we go through the rest of the playoffs, and of course once we actually enter the offseason and have some trade activity.