Talkative Sempai, Rough Shodan & Obnoxious Beginners
1. If by sempai you mean any student senior to you, then listen to those who are yudansha. Sometimes Aikidoka run on a little bit too much thinking that talking is useful. Perhaps, they are just tired and are taking a rest while they are talking to you.
2. If your sensei shows or explains the technique differently from what someone else has, then guess who is "right".
3. Years ago when I was a "brand new" shodan, there was a group of Ikkyu in the dojo who thought they were "tough". To confirm this for themselves, they went around frustrating the lower ranks on techniques. A group of us made it a point to train with these people at every opportunity. Guess what we did? Yes, we frustrated them on all of their techniques. Kobayshi, Sensei did not know or approve of our behavior. However, shortly afterwards he began to explain at every opportunity that it was the responsibility of the higher ranks to make certain the lower ranks improved. This being part of their shodan exam.
4. In relation to the above, I have known more advanced students to be injured by beginners, than the other way around. Usually this is a result of the beginner muscling a technique at the very moment the advanced student is attempting to help them learn the direction of the particular technique.
I hope these muddled musings are helpful.