i often get "400 Bad Request" apparently from cloudflare.net. is this a CDN failure? it's good that i save a copy of my post since back clicking always loses it here.

Yup. Also the 20 images in the boxes that you have to click to get access to cloudflare sites.

What web browser are you using? Do you have your user agent spoofed? Do you have cookies off? Third party cookies off? Scripts turned off? Cloudflare is checking all of that for security. Also ssl handshake.

You have to present a valid request header that cloudflare likes. Also accept/use session cookies, also have to have a valid ssl handshake. Dillo for example, won't load cloudflare sites for years now.(Not using ssl 1.3).

Cloudflare is being real picky in the name of security I've noticed.

i am using firefox 90 via polipo 1,1,1 (a proxy i intend to hack but haven't yet) running on the same laptop. most of the time posts work. the big problem is that the JS code on this site wipes out the input even when backing up to post, again. if i saved the text ahead of time, i can reload it and post again.

i wonder what cloudflare thinks is wrong on a 20% sometimes basis? i suspect it's a timing issue. a post should always skuo the cache and go to the client. maybe the client didn't respond fast enough. you can't let these just hang, forever. they probably have no connection re-try there.
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does cloudflare do the client's ssl and pass data to them, when needed, in a different ssl layer? they would have to, to know it's a post.

edit:

this post went through OK.