Is the Thief Rogue's Thief's Reflexes feature optional?

Question

The Thief gets the Thief's Reflexes feature which states:

When you reach 17th level, you have become adept at laying ambushes and quickly escaping danger. You can take two turns during the first round of any combat. You take your first turn at your normal initiative and your second turn at your initiative minus 10. You can't use this feature when you are surprised.

I'm wondering whether you can opt not to use this, such as when damage at the start/end of your turn would reduce you to 0 HP, or if you've put a condition on an enemy that lasts until the end of your next turn. For example, the pyrotechnics spell blinds creatures until the start of your next turn.

I'm unsure because the wording both says "You can take two turns [...]" and "You take your first turn [...]", where the first perhaps shows that it is optional but the second seems to say that it is not.

Answer 1

You can take two turns, but you are not forced to

The 2nd sentence says that you can take two turns, which makes it clear that the feature is optional. The 3rd sentence doesn't contradict this, it just clarifies when your two turns happen in the initiative order if you choose to take two turns. If the 3rd sentence wasn't there, both of your turns would happen at the same initiative count.

You could argue that the 3rd sentence ought to begin with "If you do" to make it more clear that the choice to take 2 turns is optional, but rules in 5e are usually written for the common case, and choosing not to take your free turn on the first round of combat is going to be an exceedingly rare occurrence.