Inquisitor, I have indeed searched for this information, and would not be asking had it been answered satisfactorily. Most threads are from 2009 and before, and some imply that the requirement has changed in the meantime. The page you mention I've already looked at in detail, and it does NOT answer my question:
German residency is not required for activation, however you need to provide a German address (which won't be proven, so you can provide just any existing address). If you have a German bank account you can enable recharging by direct debit, but a German bank account is not required for activation any longer, as it was earlier.
This addresses activation
, not online SIM purchase
. Hence, my question.