What voltages are expected/can be tolerated on USB Data Lines?
The V-USB wiki itself as you say provide a simple solution to this: Level shifting the data lines via Zener diodes. It is not a perfect solution, but I believe it's definitely better than simply putting 5V on the data lines. It might not damage your USB ports, but it is definitely out of spec, and there is no reason to design out of spec on purpose.



For details, check http://vusb.wikidot.com/hardware, the "Solution B"-section, which is also where the picture above comes from. 

What the best solution is will also depend on what the critical elements of your circuit are. You have already mentioned that the MCU must run at +5V, so dropping the voltage there is ruled out. You could probably use a level shifter IC instead of Zeners to drop the voltage at the data lines, but that would again probably cost more. 

These are design decisions you need to make depending on what you will prioritize about your design. Good luck!