I use dropbox, but it doesn’t really work for sharing small snippets/links/comments.
Pastebin wouldn’t give any alert, etc…
Instagram, Facebook, Twitter etc… would probably work, but seem somehow overkill for someone in the same room, plus not keen on the privacy implications.
Of course, email would work… it’s just fiddly. We do use email, but that tends to be for longer more important stuff.
If it was on a phone, there are a fair number of apps, or you can send by whatsapp or text message or something, but if it’s on PC there doesn’t seem to be anything that quite fits the bill.