Smite exists, but your opponent is using Protect from X. Meaning you have to do 344 damage to drain the 43 Prayer that exists. Of course, it will decrease in time, but that could be enough to use up your food and your prayer.

It could also be used when your opponent retreats. If he/she is stupid enough not to bring runes to teleport (in your opinion), then it is a simple matter to active a prayer and run towards the south. Of course, it isn't technically teleport to save your stuff, so people had to invent a new insult. It is now generally more respectable to not use prayer. If you want to use prayer, no one's stopping you, but the consequence is getting called a prayer-noob. It's similar to... let's say bribing someone to help you clear a debt larger than the bribery. Basically, you're gaining an 'unfair' (in their eyes) advantage.[No one calls the other combat type a noob, because Jagex has made it balanced so one combat type has an advantage and a weakness to one of them (although some claims it to be unbalanced). If you meet an advantaged opponent, you're screwed. But, if you use prayer, the triangle will not be in place and you could escape sucessfully or even kill your opponent. There is no more balance when prayer comes into place. Therefore, people will consider prayer to be an 'unfair' (in their eyes) advantage and therefore, labling those who use it as a noob.

Dragon Scimitar has that special ability. However, it only lasts 5 seconds, which the opponent can easily recover from. Unless your opponent is near death, then 5 seconds of vulnerability is insignificant. There is also the matter of actually damaging your opponent, which relies on luck.

You would need to spend ~1M to Ectofuntus your way to 52. This is affordable to a reasonable portion of P2P, but not many people would buy bones purely for PKing, mostly for combat levels.

You can do something about it. The counter-effect is either too low or too expensive for PKers to afford.

Forgot about this topic
To stop someone from running south, they can use a spell to stop them from moving. If you really don't want your opponent to teleport, you should be out very deep. Using a spell to stop them should keep them from getting to level 20.
There are people out there to pk, it just takes longer. You have to make a choice: Either wait a little longer for someone to come, or go in shallow where there are lots of people and risk having them tele. It the pkers choice. If you need to, get a team. If you can't, that's your problem, not the person who is teleing in level 15 wilderness.
Again, this is their choice. It is in their power to get tele-block. If they can't afford it, again that's their problem, not the person who is teleing in level 15 wilderness. If they really wanted to, they could work for it and get teleblock to stop them. How they spend their money is also up to them.
I'm not positive, but I do think that Teleblock lasts for five minuets. I can look into it more if needs be.
I have yet to see someone tele with an ectophial. I really don't think that many people know about it.
Another choice, they can get members if they want to. If their parents or whatever won't let them, that's their problem, and once again, not the person in level 15 wilderness teleporting.
If they get scammed, that is 100% their problem. I have never been scammed from a trade screen in my LIFE. You know why? Because I always double, sometimes triple check each screen to make sure that it is correct. There is absolutely no way that I will feel pity for anyone who gets scammed by simply not paying enough attention.
If you let everything that's allowed in the wilderness be allowed in the duel arena, I don't see how anything can be based on luck.
There are bugs all over Runescape, not just in the duel arena. A lot of people have gotten screwed over by them, including myself, but all you can do is report it to Jagex and wait for it to be fixed. (If your wondering what bug I had, I had one where my full grown CAT, yes CAT not kitten was asking for food. I tried to feed it but it wouldn't let me and it told me since it was a cat that I didn't need to be fed anymore. It ran away eventually. My CAT ran away. It was sad lol. There was appearently some bug with some Cats that were transfered from RS1.) Anyways, what if being able to get around teleblock with the ectophial is a bug?
That may be true, but it is beside the point. The point was that prayer was put in the game, and people have every right to use it how they want.

Dunno why I can get any quotes to work :\

Actually...I'm eating a cherry Poptart right NOW!

But back on topic

The thing I have a problem with, People attacking agility-er's
and people that get a good fight with you, using almost all your damn food, then they tele, after a waste of 5 minutes, and all that god damned food.