I've installed the WIndows 8 Skype and messenger, but it lacks RTL support:
1. Even if I write from right to left (using CTRL+SHIFT, it's not automatically goes to the right), after sending it, everything goes to the left and there is not option to change it.
2. When writing mixed text with Hebrew and English at the same message, the sentence gets mixed up and doesn't make any sense.
Since MS Messanger service has full RTL support, I can't see why Skype, which is MS software, can't have the same. Please, fix these minor bugs, and RTL people would use your software, but currently it's just impossible.
P.S. The post above concerns English UI, and not Hebrew UI. I don't understand why in the English UI there is no RTL support.
When I referred to "Skype for Windows 8" I meant the Skype app that you can get from the Windows Store app in Windows 8. You are still using the "classic" Skype for Windows application that still has a few flaws in regards to RTL support indeed.
I just tested the Skype for Windows 8 app myself with your scenario and indeed we force alignment of chat messages based on UI language chosen. I've flagged this to our development team.