I wasn’t aware that Office Communicator supported keyboard shortcuts for text formatting in the chat window.
Since I normally use RDP/MSTSC connections to a work machine (the laptop often moves around which means that network connections aren’t
“persistent”), which means that every once in a while a key like Shift, Alt, Ctrl, or Windows hangs.
That’s how I found out why sometimes the font in the chat window changed a bit: most often the font became strike through, which corresponds to Ctrl-T.
Three things that Microsoft should improve here:





