Only bad PKers suicide. Only bad PKers can't hit someone before they get the chance to suicide. There is more than enough opportunity to hit them before they get the chance. You can get a swing/arrow in when they cancel their blink to die. The only reason they suicide is to make you upset.

I see two ways to penalize suiciding.
1) Add deaths to profiles, again
2) Make all deaths (suicide, pking, bking, except spar deaths/losses (stupid how these count as deaths)) drop your arrows/bombs.

I prefer option one, but option two would be effective.

If you are in towers and have trouble with suiciders you can prevent it by spamming the bombs you pick up in the corners of the towers. The less bombs in circulation, the less suicides that occur. If they keep coming back with more, be happy you're making them waste gralats.