If you short against the box, the only thing that'll happen is you have to count capital gains as if you sold the stock regularly.. If you fail to do that, then you could get nailed for trying to evade taxes that way.
One reason I could see for shorting against the box other than for tax reasons, is if there's some major event that's going to occur w/ a company that may make it unshortable (due to many others wanting to short it), you can buy and short against the box w/ your own 2 accounts, so you can effectively short it later without having to worry about borrowing the shares or the uptick rule.
One reason I could see for shorting against the box other than for tax reasons, is if there's some major event that's going to occur w/ a company that may make it unshortable (due to many others wanting to short it), you can buy and short against the box w/ your own 2 accounts, so you can effectively short it later without having to worry about borrowing the shares or the uptick rule.