Is this part of the description of the Archfey warlock's Misty Escape feature redundant?

Question

From the Archfey warlock patron feature Misty Escape (PHB, p. 109).

When you take damage, you can use your reaction to turn invisible and teleport up to 60 feet to an unoccupied space you can see. You remain invisible until the start of your next turn or until you attack or cast a spell.

The part I think is redundant is the last part where it says "or until you attack or cast a spell". If I've used my reaction, I can't make an opportunity attack or cast hellish rebuke or a similar reaction spell, and by the time I can attack or cast a spell again, it's my turn again, so surely that's covered by the "until the start of your next turn" part?

Or am I overlooking something?

Answer 1

It is not redundant

There are many ways you could take damage on your turn, thus allowing you to use Misty Escape as a reaction on your turn in addition to (before) your Action and possible Bonus Action:

• An enemy was holding an attack or damaging spellcast that is triggered before you attack or cast a spell on your turn.
• Many ability/spell effects also specify that you take damage if you start your turn in their area effect.
• You could move before taking an action to cast a spell or attack and provoke an attack of opportunity.

The last part of Misty Escape's description is there to cover such cases.

Answer 2

You could take damage on your turn, so the invisibility could end earlier

You can take damage on your turn. For instance, you might move away from an enemy, and their opportunity attack may damage you - or you might take damage during your turn from being in a the area of effect of a damaging spell or ability. You can then use your reaction to turn invisible and teleport 60 feet away right after you take the damage.

Then, you still have the rest of your turn left... If you attack or cast a spell, it will break the invisibility. Otherwise, you'll stay invisible until your next turn starts.