I didnt found ANY information in manuals about it.
Why does data segment can be written to without write bit set in long mode?
when i load ds/es/fs/gs, write bit is ignored. base apply only to fs and gs, ok.

why write is ignored?
when i load SS, it require write permissions btw.

Correct me if I'm wrong, but it turned out that paging is the usual way to protect memory in most 32-bit OS's so segment-level protection became unused. This featured 64-bit OS's.

yes it suck but i care if its used. i must know.......

Empirically I don't know, when I did my 32 bit OS 5 years ago, I used the flat memory model so paging is a new thing to me, and I'm just setting up my memory map. What I would guess is that CODE type segments are much more critical to intrusion, data is not so much, so they ignore it? That would be my guess.