@Meanlucario
Selfcest isn’t any different than identical twins, so yes, it’s technically another form of inbreeding.
Also, I’d like to clarify that inbreeding itself isn’t the cause for deformations, but the lacking of diversity in the gene pool. Every being has some errors(mutations) in their DNA, you take account the thousands of genes on top of thousands of cells in your body, there’s bound to be errors. The reason why those errors don’t mean anything is because there’s too little and your other genes can correct it. A less diverse gene pool means that the being in question has more chance of having too many errors or those errors making a bigger impact, and too little diversity to counter it, and thus they are more susceptible to having diseases, deformations, or just generally weak. It’s why pure breed dogs like pugs are so prone to health issues, they are deformed.