Like the majority of the members here I recommend against deliberately trying to become incontinent, but it seems like there may be some misconceptions by some of those who claim to desire it. If the intent is to experience the feeling of being a helpless 6 month old then incontinence would likely help that. But this may not be the case if you are looking to realistically regress emotionally to an 18 month old baby.
When you think about the main difficulty parents have in potty training toddlers, the problem is not that the babies are incontinent and can't hold it. It's just the opposite. At 2 years most babies seem to have no problem at all holding it in for hours, and many of them do just that when sitting on a potty. This ability would not have just appeared overnight but would have been formed over time.
If you want to relive the sensation of being a toddler in diapers, uncontrolled wetting may not be a realistic part of that fantasy. Just off the top of my head, I would bet many 18 month old babies have pretty good control over their bladder and decide for themselves when to empty it. They may even enjoy that control to some extent, and, at the same time, they would have no qualms about deliberately wetting their diapers since that is why they are wearing them. Diaper lovers may have more in common with toddlers than they realize.
Just a thought. Is this something that is painfully self evident? ...or are there really misconceptions about this?