yes , you can have many communities with the same name. One on each instance. You have two mode of scrolling in lemmy, local instances and federated (connected ) instances. You can also comment in other instances. Although , be careful when you post and comment in other instances . You basically are like a tourist visiting another country . Rules and culture are different between lemmy instances. I see instances just like countries with their own laws and culture. Some countries blocks other and some make alliance and free trade and travel visas. Some instances are free for all, others are more authoritarian. Some are more conservative , other are more liberal , some are communist.