1st of all u have to use fake death in place when shops are not allowed.
after this your character should stand automaticly.

Altough u can walk and run mobs thinks u are dead and dont agrro on you.
You can hit mob and he will not attack you. You can hit dark blue RBs and u will not
earn paralize. this bug will stop work after you sit.
You can change subclass and it will be still work.

dont know on how many server it works but i know it works on abyss 7x.