The pre-determined list of login messages is, in all honesty, not great. No offence to whoever set them, but none of them work for me and many of them are similar joke-ish ones. Now, that would be more understandable if they were easier to access, to stop trolls messing with them. But 2,500 coins is a lot - you get 140 per day of voting so would need to vote for 18 days, assuming all votes went through. Alternatively, you can win 250 reacts, which happen every 5 minutes or so. Assuming you win them all (which is difficult as there is often competition) in a row through non stop play, that will take nearly 21 hours. Through a mixture of voting and reacts, it took me several hours of play a day for two weeks and then around a week of voting.
So to me, anyway, it is pretty clear that the players doing this are going to be committed enough to the server to be able to be trusted in setting their own login message. Staff should be able to intervene, obviously, and change someone's if they happen to go through all that to break the rules with their login message.
Edit: I would just like to add that many items in the list feel like they were set by and/or for certain players already, such as there being one that is referencing an old song. They feel too specific. It feels as if members of the community already had access to this feature if they were in good standing with those who could add login messages. I also would not have saved up 2500 coins if I knew what my options were. I've had to settle for (Role) (Player).