There are no taxes incurred on the gains or losses realized inside a traditional or Roth IRA when trades are executed. With a Roth IRA, the dollars come out tax free within certain constraints (age or account lifetime, roughly speaking), with contributions sourced from after tax earned income. With a traditional IRA, taxes are due when withdrawn. They can only be funded with dollars, not shares or assets. You can direct your investments with a self directed IRA for esoteric asset classes, but the IRS has strong guidelines around this to prevent self dealing as well as requiring transactions to be “arms length”. You cannot borrow against these accounts (although you can roll traditional IRA funds into a 401k and borrow against it there as a fixed term loan at an interest rate set by the plan administrator that follows the benchmark rate).
What changed? I didn't see anything in the article that says you can't buy startup (or other non-public) stock in an IRA, and if you do and it goes well, your IRA can become very valuable. If I work for a startup again, I'm definitely going to see if I can get early stock into a (Roth) IRA, because it'd be real handy if the stock does well, since you can trade in a IRA without tax consequences. Seems complex to set up though.
Can you buy and sell shares tax-free if the cash > security > cash conversions all happen inside the IRA?
What about capital gains taxes?
Can the money inside the IRA be spent?
Could you borrow against the IRA as collateral?
Can you make exotic investments or are there limitations?