One change I would like to see is not having to sell your shares in the order that they were bought. I think shares should be sold based on highest profit/lowest loss differential.
For example, suppose on Monday I buy 10 shares at 50 cents each. On Tuesday the price drops significantly to 20 cents which I think is undervalued, so I buy another 10 shares at 20 cents each. Come Wednesday, the price has rebounded to 40 cents and I would like to liquidate my 20 cent gain per share from Tuesday's purchase. However, in order to do that I must first sell my 10 shares from Monday at a 10 cent loss. Why is this so? Unless I am willing to accept a loss, I can't sell any of my shares until the price rebounds to 50 cents or higher.
A better alternative would be to sell the shares that would result in the greatest profit/lowest loss for the seller. Or just let the buyer select which shares to sell. This is good for PredictIt's bottom line as well since you get a 10% cut of profit - so maximum profit for the seller gets maximum profit for PredictIt. Additionally, it could result in more market activity by allowing sellers to liquidate and reinvest as outlined in the scenario above. Buyers would not be affected by this change, as it does not affect the sale price - just the seller's profit. Hope you will consider this change.
FIFO is pretty standard in most financial / trading transactions at least from what I've seen...
Terrible Idea! Should be the exact opposite! Sell the shares with the biggest losses first.