WowAce

What steps will reproduce the problem?
1. in bg, dungeon, or raid finder, try to whisper someone whose realm contains a space, e.g. "Alterac Mountains"

What is the expected output? What do you see instead?

notice that the chat frame shows "Tell someone-Alterac: Mountains

What version of the product are you using?

r604

Please provide any additional information below.

I looked through the api listing on wowprogramming.com (the only one I could find) and it appears the only function usable to send messages is SendChatMessage.  Since you can't specify the unit in a separate variable, I imagine that is the problem.  The same thing happens if you type a whisper manually, e.g.

/w Someone-Alterac Mountains

when you hit the space it uses what you've typed so far as the destination.  So I'm guessing there is no fix for this until Blizzards adds an api call to specify the player properly.

What the hell? X-Perl is NOT a chat UI, and as you said, the support is buggy due to Blizzard's end.

And I don't think you're on right place to suggesting such problems.

My mistake, I wasn't clear in my original post. If you right-click on a unit frame, I assume the popup menu is generated and handled by XPerl. The problem occurs when right-clicking a unit and selecting "Whisper" when that unit is on a different realm and that realm has a space in the name. I did not try without XPerl to see if Blizzard's default UI has the same problem.