Can you retrain the Magic Initiate spell using the Spellcasting feature?

Question

This question got me thinking about the mechanics of the Magic Initiate feat when you have class levels in the class into which you were inducted.

Among the classes you can pick with this feat are the Bard, Sorcerer, and Warlock, which know a limited number of spells and all have the same statement under Spells Known.

Additionally, when you gain a level in this class, you can choose one of the [class] spells you know and replace it with another spell from the [class] spell list , which must also be of a level for which you have spell slots.

The term "learning" is used both to describe new spells acquired on level-up and the spell acquired through the feat. This would seem to indicate your Magic Initiate spell counts among the spells you know, and is thus eligible for retraining if you learned it as a spell of your class.

An odd change in wording occurs during the Magic Initiate feat description (emphasis mine):

In addition, choose one 1st-level spell from the same list. You learn that spell and can cast it at its lowest level.

This generalization in describing the learned spell's level seems to imply that there exists a scenario where it would not be appropriate to restrict the spell to being cast as a 1st-level spell. Could one of the charisma casters retrain Magic Initiate into a higher level spell, which they could then cast once per long rest without using a slot?

This would turn an otherwise unexciting feat into, effectively, a Mystic Arcanum for Bards and Sorcerers. This seems too powerful to be intentional, but the feat description appears to have gone out of its way to permit it.

Answer 1

This looks to be entirely up to DM discretion.

There are two equally valid positions on this and the rules do not refute either one.

The first is that this is a completely separate spell, and slot, and that the two have no overlap with your casting class. The spell you learned and the slot you obtain are kept separate from the class spells if you have levels in that class.

The second position is that it is a class spell, from your class list and you can retrain it as you would when you take a new level in that class.

The second position is mildly problematic in that you can continue to obtain higher level spells with the retraining, and it may lead to this MC being simply the obtaining of another 1st level spell slot, rather than feeling like a mini MC.

The first position is problematic in that it introducing additional bookkeeping and may be perceived to be overly harsh and pedantic.

In my games, I think I would allow the MC feat to simply be an additional first level spell slot and allow the spell to be retrained if it's from a class that allows that and you take levels in that class. I would probably not make them remember which spell goes with their MC beyond that the extra slot must be a spell from that class. This may be too lenient for some games though.

Answer 2

You can retrain the spell because the Magic Initiate Feat's spell counts as a [class] spell. However, you would lose the ability to cast it without a spell slot.

This argument is for the Rules As Written. It is quite clear that this is not intended, as has been stated by lead game designer Jeremy Crawford:

Magic Initiate doesn't provide a way to replace its spells. A DM might allow them to be replaced when you level up.

---

We note Magic Initiate's wording:

In addition, choose one 1st-level spell from that same list. You learn that spell and can cast it at its lowest level. Once you cast it, you must finish a long rest before you can cast it again using this feat.

So we have at least learned the spell, but is it a [class] spell for us?

This Q/A ("What makes a spell being cast considered to be a {class} spell?") establishes the metric "if it appears on your class' list it is a class spell for that class". It is on our spell list so it is our [class] spell. But perhaps Magic Initiate is somehow an exception to this rule?

We know from this Q/A ("Can you cast a magic initiate spell using spell slots?") that you are in fact able to upcast magic initiate spells.
Looking at the spellcasting section we see it states:

The [class] table shows how many spell slots you have to cast your [class] spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell's level or higher.

Because you can only cast [class] spells with spell slots, and you can cast Magic Initiate's spell using your own spell slot, then Magic Initiate's spell must counts as a [class] spell.

The spellcasting section states:

Additionally, when you gain a level in this [class], you can choose one of the [class] spells you know and replace it with another spell from the [class] spell list, which also must be of a level for which you have spell slots.

As shown above the Magic Initiate feat's spell is a [class] spell. And thus you are able to replace it with another spell on your [class] list.
But can we cast this new spell without a spell slot once per long rest?

Magic Initiate states:

In addition, choose one 1st-level spell from that same list. You learn that spell and can cast it at its lowest level

Both of these refer specifically to the spell that you choose when taking the feat. If you were to swap out that spell for another the new spell would no longer qualify as "that spell" in the text. Thus you would not be able to cast a spell that replaces your Magic Initiate spell without expending a spell slot.

---

In addition our replacement spell does not even have to be a first level spell, this is because the clause in the Magic Initiate feat only applies to the spell you choose and the clause about swapping out spells specifically allows you to swap out a spell for one of another level so long as you have the spell slots to cast it.

---

Because a spell learned through Magic Initiate is on your [class] list and it has been shown that you can upcast spells learned through Magic Initiate (further evidence that it counts as a [class] spell) it follows all other rules that your [class] spells do.
Namely, you can replace it with another spell just as you can replace any other of your [class] spells.