From my experience Orca is spot on the money. SARS will not see you as one all encompassing entity in his example - as an individual you are well within your rights to own a property on capital account (primary residence) and a second property on revenue account (rental property). These are treated differently for the purposes of your tax submission.
The same goes for your investment portfolio versus your trading account (recommended that you keep them separate). Your intention in your investment portfolio is clearly capital in nature, as will most likely be evident in your treatment thereof (ie you won't necessarily be buying and selling, in other words trading, with this account). While your intention in your trading account will be one of generating revenue. It all comes down to intention.
Believe me I follow your logic, but here's the rub.
You are a normal working person who receives a fixed monthly salary (income), you have an investment account with a broker and you buy and sell shares within the parameters of SARS dictates. Now you open up an SSF account with the same or another broker and you trade over this account, and lets say you make a profit of R100,000 in the year (arbitrary figure). When you get to the portion stipulating your income for the tax year you will have to declare - your salary, any other benefits and any other income. Now the R100,000 profit becomes income, and could be taxed at your marginal tax rate (maybe as high as 40%) or the tax man may tax you at a rate commensurate with your net tax position - which could be a lower overall figure than the 40%. If you know before hand which way the tax man is going to access you then at least you can decide whether to claim deductions for the trading leg of your portfolio - so that is what I am trying to determine before writing or discussing with SARS. What I don't want is a witch hunt after entering into discussions or correspondence