Hey only the account that submitted the game can vote on others. All our team members are not able to vote ^^

It also does not show us contributing to our game if we write comments.

This is intended. Only one person per game is able to vote. Otherwise teams would be in advantage in comparison to e.g. Solo Devs, right? ;D

About the contribution I don't know, why it is like that...but I think it is the same thing: Your game would simply get more "attention" if it is shown in more comments etc...