Is the holy symbol that a cleric or paladin can use as a spellcasting focus a discrete object? Does it stop being a discrete object when the player decides to bear it on a shield by inlaying it?
For context, a player wishes to enchant their holy symbol (borne on their shield) with a Continual Flame spell. As such, the shield would not be entirely aflame, but the holy symbol would, forming a fiery shape of their god's iconography.
Helpful References
Holy Symbol. [...] symbol carefully engraved or inlaid as an emblem on a shield [...] the caster must hold it in hand, wear it visibly, or bear it on a shield.
—Player's Handbook Ch. 5 (italic emphasis mine)
For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone, not a building or a vehicle that is composed of many other objects.
—Dungeon Master's Guide Ch. 8
A flame, equivalent in brightness to a torch, springs forth from an object that you touch.
—Continual Flame