The reality is, serial posters, and there are several on the boards, will continue to be serial posters. No amount of reassurance or advice will change that. You can continue to try and while it's noble, all you're doing is feeding the dragon. It doesn't matter if it's a slap upside the head or tea and sympathy. It's just not going to change nor help the OP.
For whatever reason, they are unwilling or unable to help themselves and this forum is essentially being used as a sounding board and public blog of their illness. Sadly, some will be this way they're entire lives. Even with professional help, some will never recover.
Also, even when those that have been around for a while see the patterns and refrain from posting, there will always be a fresh supply of members who aren't familiar with the OP's history that will feed their dragon. Perhaps that's part of the appeal to them on the forum. There is an inherent attention seeking aspect as well whether it's intentional or not and a constant supply of food and attention. The stray cat analogy applies.
The best advice
(should you feel compelled to reply) should be to seek professional help and/or to guide them towards the
ample resources on the site.