I have a couple of thoughts after several games about a minor UI tweak for auctions, similar in spirit to preventing bidding against yourself (which has already been discussed). A minor issue I have experienced is inputting a bid slightly higher than I intended by clicking slightly after another player's bid goes through. I have 2 suggestions to help with this, one of which is something you likely already do.

First, I'd like to see a client-side delay (half a second or so) after someone bids on an auction before you are able to click the button. This could be visually clarified by changing the button text to "processing" or something like that. It doesn't need to be an actual rule in the server/processing code, just a UI adjustment for the client. Half a second is longer than human reaction time, but still very short overall. This delay could probably be shortened even further if needed; the only point is to ensure that a player didn't start moving their finger before seeing the update.

Second is something you probably already do, but I'll mention it anyway. The request sent to the server when a player bids on an auction should be tagged with the value that their client was displaying as the current bid. The server should ignore bids with outdated values, since the user did not intend to actually bid at the newer, higher price. They can click again if they really want to bid; there is more than enough time before an auction closes to allow that.