i didn't really understand , what i mean is :
user dir:us/er/user2/
posts file:us/er/user2/posts.txt
replies folder:us/er/user2/replies/
replies for post 12us/er/user2/replies/12.txt

(txt extention is only for example)
inside a post file posts stored as :
id1|time|post_content\n
id2|time|post_content\n
id3|time|post_content\n
if i want to read the last few post's , i will use a read backwards module, or something similar.
the replies files have the same structure as post file only with name of the user replied.
id1|time|user|reply_content\n
id2|time|user|reply_content\n
id3|time|user|reply_content\n

I just wanted to know what is better , to store it like this or to make a file for each reply/post ?