Messages: your mailbox
Messages is just for chatting with another person — it's separate from offers on purpose.
Messages is your mailbox. It's where you have a conversation with another person — ask a seller a question about a crystal, work out a detail, or say thank you. Find it under Messages.
Messages are only conversations. That's on purpose. Real money decisions — like offers — live in Activity, not here. So a friendly chat is never mistaken for an offer, and you'll never feel like saying "I love this!" accidentally committed you to anything.
Want to make an offer or buy? Do that right on the crystal's page (Make an offer or Buy now), and you'll see it tracked in Activity → Offers.
A quick rule of thumb: talking → Messages. Buying, selling, and offers → the crystal's page and Activity. Open Activity from Updates in the top bar or side menu.