I think you're supposed to press on the .?123 key, keep holding, and then slide your finger to the comma or period. I assume pressing space twice inserts a peri

I think you're supposed to press on the .?123 key, keep holding, and then slide your finger to the comma or period. I assume pressing space twice inserts a period, too. Disclaimer: it's been a while since I used an iPhone, this might be out of date.