You guys should understand that skilling is useful for any class.
While a mage can buy fishes and train its magic level if he wants, a skill based class should be able to do the same.
If you guys don't want it to happen, make it harder.
Make it lower to skill if you are afk.
Make it better to don't skill, just level and, in that way, you would gain more.
There are PLENTY of ways to make the player itself forget about training and keep playing the game.
Choosing the shittiest way of doing that, in that case, PROHIBITING SOMEONE TO TRAIN AFK, is not gonna work out.
Seriously. Get over it. If you want people leveling and not training, make it count.
Don't fucking ban or reduce someone's skill if he is training while afk.
If someone is training using bot, DELETE its character.
If someone is training in necronia, while playing another game and just coming back so the character don't get kicked, nothing should be done.
Also, if someone is training AFK, he should be aware of dying by a PK, too. I myself would kill someone who is AFK training.
Anyway, there are a lot of ways to make someone forget about training.
And prohibiting afk training isn't one of these ways.