Whenever you get a new whisp chat it will straight go to a separate tab instead of staying on the main chat tab, if you close it or /reload and the same person whisp you again you will not be able to see the chat, it's going to be empty and you'll have to close the chat and ask whisp the person again to fix it.

When you trade to move trade or general tab to a separate tab it will not work, the tab will be created but the chat will still be on the main general chat for all other normal chats, a way I found of fixing this is disabling Glass, creating a new tab for Trade/general/guild chat and enabling Glass again, that's the only way of doing it.

There's the photo of how the separate whisp window looks if you close the whisp chat and they whisp you again. it looks like that. You have to close it and whisp the person back to recieve more whisps but the old whisp chats are gone of course.

These appear to be 2 separate issues.

I'll address the first part (new whisper chat) in a PR here shortly. Consider creating a second bug for the other piece (moving tab, trade chat).