Good one, that's exactly what I did, but you're too quick to do some extra research because you're desperate to put stuff on me.
If I only posted that first post, I would be an starfish, or if I added that it was from past experiences, I would still be an starfish. Well forget, you're not giving me any choices.
If you would have said right off the bat, your first post in that topic: "I've done something like this in the past, it didn't turn out as well as I thought. You're still welcome to try but it may not turn out like you think." That is helpful advice, its showing that you aren't completely shooting down his idea, but warning him it may not be as expected.
But since you host your New Year's server, you posting "It will get less then 25 people" immediately, without mentioning your past experiences, comes of as you shutting him down because he is doing an idea like yours.