That is a great way of looking at it, and to be honest I probably should have weighed the pros and cons of public bans themselves, as opposed to simply talking about why it's not doing that much harm right now, from what I could see. However, I've reconsidered what I originally said, and yes, it does actually appear like there's nothing to be gained from displaying ban messages.
No one's going to leave the server because "they removed public ban messages!", but they could leave due to harassment as a result of this. Of course, one could argue that the problem lies with troublesome users here - although, in all honesty, it seems like the thing that's happening here is that we're creating problems that don't even need to happen.
So I suppose my final stance will be that no, this is an unnecessary feature that doesn't really benefit the server other than providing a short second or two of laughs for some players, and certainly won't encourage donations.
But allow me to digress here and note that I absolutely agree with your stance on being family-friendly. If I remember correctly, someone discussed this with Fuzzlr, and he used the defence that he wants to make MeepCraft "a safe environment for all ages" (not exact words, but I don't think I could find the post if I tried, haha).
And with that, there is a severe misconception, that being the fact that little kids do not already know swear words and are not exposed to anything inappropriate. Small children have proven, time and time and time again, that they have very little respect for their peers online (they believe they're anonymous -> someone angers them -> they start using all of these new cuss words they've picked up), or at the very least, that they do not have the maturity necessary to be contributing members of an online community.
I'd love for the server to be open to players of all ages, and it still would be even with looser restrictions. How about those kids who don't actually know inappropriate language yet? Although rare, those kids are likely even younger than the kids I've already discussed - and it's a common theme among children to not follow the rules. Whether this is expressed by scamming, being rude to others, stealing, griefing, they've really done it all. Not that this isn't a problem with players of all ages, but very rarely is there a child able to act maturely and make themselves worth keeping around in a community.
At the end of the day, MeepCraft is a business. And, as you've expressed and I'm sure you already know, small children are a playerbase that really are not worth catering to; they provide very little financially other than begging parents to donate, they cause a large amount of problems for staff, and they simply seem to have difficulty following rules. Likely a more controversial point, I'd like to mention that this is a Towny server. Most of the time, small children lack patience and they do not work for things. Instead, they would prefer to simply receive things now. This is why minigame servers are still hugely popular - along with the average age of Minecraft players worldwide decreasing, minigames are becoming more and more attractive to those who do not wish to work towards a project, which is the main goal of Towny.
Lastly, thank you, Deinen. It's always nice to see your posts since they are always rational and provide a viewpoint that I think MeepCraft really could always benefit from hearing.