This thread shows that Ponychan supported two consecutive spaces, neat:
https://dweb.link/ipfs/QmPcSmBqfB78prJZbCdXGNS1q4th7YXbgQAZtGukjgvo1w/pony/res/36833126.html
https://web.archive.org/web/20240119174452/https://bafybeias454lhrn5ge6ysqscvt6akulryaknm2urojvzsbl6mq6fytkumy.ipfs.dweb.link/pony/res/36833126.html

Or did it? Doesn't have two consecutive spaces in here:
https://web.archive.org/web/20231213060219/https://www.ponychan.net/pony/res/36833126.html

Perhaps those are backend files which I got from that one guy uploading raws to IA. So then maybe the frontend/CF/whatever modified the HTML to remove double spaces. Not sure what the answer is.

I know that 4chan replaces /\s\s+/ with /\s/, I'm guessing Endchan does the same. Two spaces between here: -> <-. Also, check 'em >>9400