Because you are a such a dangerous person ,lci wale bhi aapse darte hai isee liye aap jo type kare ho wo automatically logout ho jata hai
This is not your problem ,this problem is applied to all members why?
Because of safety reason, whenever we type a long answer your activity in lci is none at that time because you type it ,so for security reason lci software will automacally logout ,and you submit the post a time you logout (at that time you have to click previously and click log in OR type your anser in word or after sometime click login in another page and thereafter submit.)
This is not a technical problem ,everyone including me faces this .,you said" I type a long reply to any post" it means your activity at that time in lci is none so the software automatically logout ,this is for security reson .This type of seurity also found in another site or company sitew also.