What type of distribution package are you using (batch, EXE, MSI)? If MSI the reboot and ui information is handled by the delivery method. So make sure your delivery method is setup to never reboot.
Office communicator is an MSI.
Delivery method was set to Reboot 'only if needed'
For uninstall, I would use the following command line switches, assuming you want it to be silent...
/x /qn /norestart