Blind bidding is bad because it doesn't allow people to see what the actual market looks like, and no one can make proper decisions and it would hurt market efficiency and cause large price gaps.

A lot of these threads seem to be made by people who feel they are entitled to large profit margins.
Check FFXI AH. You can see markey history and therefore, market health and profitability, but you can't see what each individual seller lister their items at. Which means for constantly selling items, like food (Specifically Sole Sushi) it stayed at a constant 30k for a stack of 12 (this was prices when I played about 2 years ago) but people could list them for 29900, 29999, 27000 and people would place bids around 30k until they were able to actually purchase the item.

Yeah this lead to undercutting, but it certainly wasn't as rampant as it is here where I have to change my prices 5 times a day to compete with people who undercut by 1 effing gil constantly.