Numbered lists are usually better than bullet-point lists, especially on Slack and Twitter. Advantages of numbered lists: 1. They make it easy for people to refer to the points you made. 2. They encourage you to think about the priority of the points you’re making. It’s easy to underrate point (1). If you make it easy to respond to what you write, you'll get more responses, and they will be easier to understand and perhaps of higher quality. If you don't want to express priority, use an alphabetical list. This is less important in contexts where it’s easy for someone to add a comment to your text (e.g. a Google Doc).