I just want to say these stamp auctions are run a lot cleaner than the old methods used 50 years ago
agent bidders had a in bed relations with the auction houses
Yes, so I have heard.
Even bidders who sat in the room made agreements not to bid against each other
Yes. I worked for a few auction houses back in the day, and this absolutely happened. If we knew this was happening, we banned those bidders from the auction. Sometimes, 'for life'.
Back before the internet, and in the era of mail-in-bids, phone-in bids, in-the-room-bids, etc, at the end of the day before the sale, we would create a printout (dot-matrix printer!!) with one entry for each lot in the sale. Each entry had info on the lot, consignor/owner info, a list of the top 3-5 bidders including who, how much, 'rating' (something like the company's own 'credit rating' of that client) and whether they were doing 'OR' bids or 'LIMIT' bids, plus probably 20 other bits of info per auction lot. The boss would take the printout home and decide who was the high bidder and at what level (accounting for tie bids, rejecting 'ridiculous' bids, and rejecting bids from bidders that were not welcome to bid but did anyway, etc), so there was a relatively 'clean' picture for the next day. In the end, all this activity was (like it or not, rightfully) attributed to 'auctioneer discretion'. You know - that phrase that is in every auction house's Terms. So, honestly, if you were a problem bidder (slow payer, non-payer, or something as simple as being argumentative) it was at this point that the cards were stacked against you --- a good customer ALWAYS won a tie with a problem customer --- and it was attributed to 'auctioneer discretion'. Like it or not, all legal. If a problem bidder was the high bidder, all alone, he got the bid, assuming he wasn't such a problem as to be a 'banned' bidder. As to outright illegal activity on the part of the auctioneer, I never saw that where I worked. As an insider in the industry, I heard about the illegal stuff at other auction houses. Probably the equivalent of 'rumor', so nothing to swear to. In the least, it opened my eyes and showed me what to watch for. When I left the industry (and 'reverted' back to being a collector) I avoided those rumored companies like the plague. In the decades since, these rumors 'got out' and these companies are now widely known for their shenanigans. Look on other threads if you want to know. I will not pass along rumors, which is all they are from my POV. Never have I seen any of this behavior first-hand, so they are rumors AFAIK.
One big (HUGE) difference between now and then is the speed with which things happen at auction. The printouts that I witnessed probably don't even exist anymore. There is no 'overnight' in the auction industry - bids happen at all hours of the day and from bidders all over the world - and most bids (I suspect) are now received in realtime, so the idea of 'picking and choosing' by the auctioneer could really only happen in realtime - problematic at best with all the other things happening during the auction.
The 'signs' for some of this behavior have been discussed at length in this thread. One of my mistakes (at the start of this thread) was trying to make hay out of what APPEARED to be this shady behavior. Looks can be deceiving. My apology to Modern Stamps was prompted by my misinterpretation of the APPEARANCE of the auction action. Again, I cannot stress it enough, looks can be deceiving.