I spent a large portion of my time implementing promoted posts excluding posts that had passed their payout time. I'm wondering if I was correct to do so!

Yeah, it's arguable. Some people might be annoyed at clicking on a link to a post with an expired payout, so if we include the expired ones, it's probably also good to also indicate whether they've already paid out or not. Fortunately, we can just experiment and optimize over time. I'm actually planning to eventually calculate a "suggested voting percentage" based on factors about the author and the post, so I'll stuff that value with zeros on a paid out post.

I noticed all of your messages to @null whilst I was coding - now I understand what they were all for!

Lol. I can only imagine what you were thinking. 😄

I convert SBD to STEEM in order to prioritise which is "most valuable" 🙂

I do this conversion for the coloring, but I divide STEEM and SBD into two separate time partitions. I have been debating whether I should keep doing that or just collapse it into a single list and a single time slice.

It's very doable and how I approached my choose-your-own-adventure project. I even went to the effort of encrypting the messages stored in the metadata so that people couldn't cheat 🙂 It's a fun project but my codebase was so horrendous that I stopped working on it fairly quickly. Perhaps I'll revisit the idea - motivated by what you're doing 🙂

which brings me back to the keys/security problem that you mentioned in your reply to @moecki @o1eh (sorry - no idea how I managed that mixup!) from your own post. 😉 At the rate I'm going, this is months or years away, anyway.