Outlook interpreting CTRL+DEL as "Ignore Conversation" instead of deleting the next word.

This is new behavior that started yesterday. I use Control-Delete a lot while editing messages, but suddenly it started deleting & ignoring my email threads instead of editing the text.

Microsoft® Outlook® for Microsoft 365 MSO (Version 2408 Build 16.0.17928.20114) 64-bit

I can't find anything on this Googling around or looking through the Community posts. What changed? Or what did I change by accident? Where is the setting to disable this feature? The ONLY keyboard shortcut that I EVER want messing with my email threads (instead of just editing the text) is CTRL+ENTER to send.