Can you get scammed sending a Guaranteed reply on Lymion?

The risk people usually mean is paying for a message and getting nothing back: no reply, no refund, no recourse.

Lymion's guarantee exists specifically for that: if the creator doesn't reply within 5 days, the price is refunded automatically, without you having to file a dispute or ask for it.

The only part that isn't refunded is the service fee, which is disclosed before you send.

You're also choosing who to message from real, browsable profiles, not being auto-matched to accounts you can't evaluate first.