> This is why, if something is important, I take it out of email and put it into a document people can reference.

This is how things should be done, regardless of which medium is used to discuss the project. Without isolating and aggregating the final decision of each thread, there is no way to determine what everybody has agreed upon as the final product without looking back, which quickly becomes onerous.

Things get messy when you start having different versions of each feature, but that doesn't change the concept of using email/Slack/Discord/text/etc. for discussion and a separate "living" document for formalizing those decisions.