The value of stocks fluctuates every second. Sometimes wildly.

Weakest of the many weak arguments.

Let’s do the bog-standard obvious and sane thing and pick a single point in time, once a year and use the value then. Maybe, i don’t know, close of market on the last trading day of the year. At which point it won’t fluctuate again until the new tax year. Then, we can call it “mark to market” because we’re marking the value to the market at a point in time.

Finally, we stop with silly bad faith arguments because fluctuations in stock have been successful taxed for decades. This is how day-traders pay taxes, and it’s not even a little challenging to do.

Not an issue. If you trade section 1256 contracts, the current tax code already requires you to report unrealized gains by calculating the gains as if they are sold on the last day of the tax year. Brokers have no issues calculating that and reporting that single number to the IRS.