Potty Game: Five Words (Vol. XIX)

When Snape is explaining to Bellatrix why he didn't simply kill Harry when he first arrived at Hogwarts, he says that in the beginning he was watching to see if Harry showed signs of becoming a powerful Dark wizard in his own right. Of course, that could have just been a line to convince Bella of his allegiance, but it might also have crossed his mind. LV did see baby Harry as a threat after all.

Well, if the thought has ever really crossed his mind, it was probably at this point. He will soon see that Harry can't handle an enchanted broomstick, after all.  

I was thinking that we don't really want to recount the conversation with Hermione and McGonagall, so perhaps we could just point out that while Snape was thinking his thoughts he wasn't really giving his full attention to the explanation Hermione was giving, or something like that.

No, we don't want to recount that conversation. It is enough to indicate that some conversation did take place.

Maybe he is beginning to realize that he is bleeding and that his leg hurts?

... these, who needs the monsters of the Forbidden Forest? Just an idea. Feel free to ignore it.  

Oh, I agree that he doesn't want to let anyone know about his injury at this point, but he probably feels the pain, and if he has lost blood, he must be exhausted or worse. By the way, Minerva may notice something nevertheless if Severus is limping and his robes are bloodstained. Then again perhaps Minerva is too shocked to pay attention to further details at the moment. They still have to get rid of the troll and stop the leaking of the pipes.

... hide his limping or a wince or an expression of pain flickering across his face?

I guess they need a spell similar in effect to Waddiwasi!  

Snape could suggest that he accompany Quirrell to the hospital wing - firstly so that he can continue to keep an eye on him, and secondly so he can get medical attention himself without drawing attention to the fact that he is injured.