Which of the features?
For templates I would think just long pressing a draft and then there'd be an icon to pin it next to the icon to delete it. Maybe pinned drafts are also on top of the draft list. I've used templates before for example in my posts about The International on the Dota2 community, where you need to post something very similar repeatedly.
For automatic deletion I was imagining it happening in the background. When you tap an unpinned draft from the list a silent condition is set, and if you press Send while that condition is set then the draft you tapped gets automatically deleted as you send the comment/post. Does that make sense?