Agreed, if it's not your primary purpose for having the account then it should be fine. I did a bunch of FX through them not long after opening mine, and they sent me a polite email telling me that I shouldn't do that, which was fair enough. Much better than the "freeze account first, warn later" attitude that many other financial companies seem to have.
Now that I've been investing with them for a while, they don't seem to mind.
Now that I've been investing with them for a while, they don't seem to mind.