With regards to the water bottles, some people DO need to carry water for a 10k.. .
No matter how well hydrated I am I always seem to get a dry tickly throat and have to sip water when it gets like that otherwise I end up in a big coughing fit that progressivly gets worse until I'm nearly sick. Thats not good at the best of times never mind mid race, there is nothing "wrong" with me medically or otherwise, its just how I am.
I also suffer with asthma and trust me on this, its always nice to have a drink after taking my inhaler but my doctor also recommends it to help prevent getting thrush in your throat which can be a side effect of taking these meds.
People who run in groups so you can't get past really irritate me though, there were loads of run/walkers doing this at my last race on a narrow path.
I like people shouting encouragement, I've found it can help when your struggling. I also think its nice to thank the marshalls or at least smile at them on your way round if your too tired to talk.