I'll try and update this opening post as often as I can.
List...
pcb_archives-san - sells conversion roms (mostly sega 16/18) but pcbs are always conversions.
Jasonmelaniebarry_2000 - not dishonest per say but doesn't really tells the truth. Hides important facts.
Mengxiangjia9328 - Sells faulty stuff as working. Avoid.
Namazu_4278 - Sells faulty stuff as working. Takes screenshots from internet and claims working. Avoid
scramble1982 - Passing on conversion as originals. Also often bumps auctions with second account.
Yamatoku_office - bumps auctions with second account.
isikawagrom - sometimes sells converts without specifying it
hiyoko_studio - sells converts, but he specifies it
g_collectionjp -sometimes sells converts without specifying it
daniel3tb - sometimes sells converts without specifying it
kogi415 - sometimes sells converts without specifying it
jujuyokointokyo (aka GreatFiveAura on eBay) - sells the same items on YAJ and eBay, but doesn't send them if they're sold elsewhere and doesn't refund.
wzshv72401 - Sells conversion without actually stating it. When this guy says junk, they are really and truly junk. Like dead customs impossible to fix kinda junk.
ecolo_tokyo-san - Junk stuff is really and truly junk with this one. Don't expect untested stuff to just work

aqpuf03796 - Sells broken stuff as working. I.e No sound on pcb and shows pictures of it working. Obviously you can't see if sound is working from pictures

Taupaipai3636 - Sells conversions saying it's original.
tetsu_1988_cocktail - sells copied arkwrok as original.
Lets keep this rolling!