WhatsApp supports real italics with underscores, but the markers show up in notifications and in some desktop clients. Unicode italic avoids the markers entirely.
Use Font Style when the message leaves the app: a caption, a status update, a copied line for a screenshot. For ordinary chats, the native formatting is still cleaner.
Test on the recipient's device if the message matters; fallback glyphs vary by phone.
Written by FontStyle - more at fontstyle.io.