Strange iMessage text bubble

Hi Tom Kramer,

You can reproduce the issue by replying to a specific message that does not show in the white bubble with the blue letters. To get the reply option to appear for the specific message you want to reply to, you can follow the steps here: Send an inline reply to a message on Mac

Best regards

Thank you for the reply Tom Kramer!

It looks like you were replying to a specific message. Were you replying to a specific message? Look here:

Reply to specific messages on your iPhone, iPad, and iPod touch

Cheers!

Hi Tom Kramer,

Thanks for connecting with us here in Apple Support Communities. We understand that you notice some white bubbles on messages that you sent from your Mac. This could happen if you use any additional message features when you sent those messages. Check out the link below.

Use Messages on your Mac

Take care.