Just to see if I understand hallmark, if I set it on a server that server will be "mining" on behalf of the hallmarked account without needing to unlock the account?
No.
Ok...

Can you spare a few more words to explain what it is then? I feel like it is something terribly obvious given the lack of verbose explanations, but I honestly don't have a clue.
Ah, sorry. Hallmark has noting to do with the mining. Its purpose is to mark legit nodes.
Ok, fair enough. But the reason I made this confusion was:
HOST_WEIGHT - "weight" of the host, u can have a lot of hosts marked with the same account, weight defines what part of the balance will be used (weight/Sum_of_all_weights). If u have only 1 node then it will use 100% of the balance
So, is this weight a 'how much the network should trust tis node'? I just assumed 'part of the balance will be used' was pointing towards mining.