[nikofeyn]

getting a price better than your limit isn't better than your asking price. you state i will accept nothing less, which is typically priced lower than or close to the market price. so your asking price is really the market price but with a safety net. it's not really a courtesy at all that limit sales go for higher than the limit.

and oh goodie, i made an extra $50 on my trade because of some algorithm. thank god for that.

[encoderer]

Actually, the liquidity providers who are filling orders passed from your broker will give you a better price than the market NBBO (or your limit) by a couple tenths of a cent. You can google it to read more. It's generally called "price improvement". The main reason they do this is to capture order flow so they can use that knowledge in their own trading.