So I just joined this server today, I was really impressed of that everything was done in vanilla minecraft (I did /plugins and there was nothing), I can say that this server is the best vanilla survival server, I was shocked because it had everything like a plugin, tpa, sign shops (instead of using villagers), balance (some servers like to use unobtainable items), and a nice welcome message. However I did find a bug in the end, so if a player walks out of the protected area, they turn into survival (that's normal), but when I walk back into the protected area, I am still in survival but not in adventure, meaning players can just destroy torches and even place lava! I suggest expanding the protected area to at least 20 x 20.
Edit: You should really give people at spawn like resistance and instant health, like using a command block and make the time of effect infinite. Because I got killed by a pigman coming from a portal at spawn.