Yes, very true! I kinda got busted by some people who saw my stage and lvl and got suspicions, but I managed to chat my way out of it. but now my stage and lvl is too insane, so I never use chat... And hey! We're exacly the same lvl and stage!
But very good to know that you can use atk and speed on guild boss - how much dmg and speed multi did you use? (I always turn everything completely off just to be safe, it's not like you gain that much for a few extra stars..)
And are you connected to the stage rankings? And you say 3xx stage? I'm at 14k stage, what is 3xx? is that your power level?