To kieranchocian, you can't get the seed anymore, its impossible. The only way to know is have a backup of the seed written down somewhere, so that rule is not needed, and if you dig for the materials by this method, it will still be considered to be x-ray hacking because of the way you got the stuff(diamond, iron, coal, etc).
To aquad1, Too Many Items is not a hacking item, its only purpose is to spawn items in for the player, but the only way to achieve that on the server is to have /give enabled, which its not. Also, its allowed in creative, since it gives you the same option to get blocks. Items that are not obtainable via the in game creative menu though that are listed in the Too Many Items menu will still be unobtainable. Slime chunk finders only work if you know the original seed of the map, which very few know. If you need a slime chunk, ask a friend to help you find one in the area if they know the seed.
To TheZaqwsxz, if a 1x1 tower was built only for the purpose to see around a large area, and left alone after that purpose, then I can see it being a problem and possibly bannable. I would need Zerg's input on this to see whether or not this can be considered a big enough problem where people would have to be punished for it. Also, cobblestone structures are allowed. If you do not like the look of cobblestone, get a texture pack or alter you jar file by changing the terrain.png so that cobblestone looks different and in move favor of your taste.
To Aceflamingo23, if you see fit to complain about a ban you do not believe was correct, post a ban appeal. Otherwise, do not post random bull-crap on the forums just because you are pissed off.
More input is nice