I met a guy in the UK a while back who was a trader (profitable as far as I could judge) and had been an accountant. He had an interesting take on this question.
Basically, tax authorities don't like classifying trading profits as income. If they start letting people treat trading as an income and since lots of people loose money trading those people will be able to submit lower incomes on their tax return and the tax take overall will drop. They will also be able to claim expenses relating to trading as deductions.
So in general, tax authorities don't like to let too many people claim trading as a source of income. To get trader status and have profits and losses treated as income for tax purposes you more or less have to be managing money for others.
I'm still not sure I understand the minutia of his explanation but he was a daytrader; trading was essentially his primary source of income and he claimed he paid capital gains tax on profits. (he had a small scale trading education business on the side and I suspect part of this may have been something to point to if the tax authorities ever came knocking)
This may be the line your accountant is taking.
Based in Edinburgh but originally from Dublin and am over and back. If you are interested in meeting I'd be happy to get in touch. Still finding my way in this thing called trading.