I have a colleague who I don't believe has worked with Slack or similar services before. We are on the same team and same level in the company heirarchy.
This colleague DMs me frequently to ask questions, which is fine and expected. However, they're in the habit of sending 2-3 lead-in messages before their actual question and 1-2 messages thanking me for my response afterwards. I don't want to be rude or discourage them from asking questions or making friendly conversation, but this is obviously quite distracting. They also tend to send a second message to a channel if they've missed information in their first message, rather than editing it or starting a thread, and tend not to use threads unless someone else did first.
The extra notifications and waiting for follow-up adds up throughout the day, but as I'm not this person's supervisor, I'm unsure how to approach them to send them a Slack etiquette guide without being horribly rude. It seems like a petty thing to bring up to our mutual manager.