I’ll definitely grant you that quantitative easing complicates the picture, but i it does so in ways far more complicated than you describe: firstly, the ECB buys at secondary-market prices, so the “flight to quality” effect is still there, albeit perhaps in muted form; furthermore, keep in mind that the ECB can and probably will resell those bonds that it does purchase at a later date when it will want to wind down it’s balance-sheet. Other effects also apply. Negative yields however probably do represent a true aversion to risk on behalf of investors, in some capacity or another.