Mac Mail (Sequoia) Copyright & Trademark Symbols in text autoformat extra large size (48pt)

To begin, I'm somewhat annoyed to be even asking this question here. I've asked Grok and ChatGPT to no avail. I'm aware that time is the fire in which we burn.

I use the copyright symbol © (option-g) all the time as a pseudo signature. It's kinda part of my personal email style, a sort of trademark (™) I've been using for probably 20 years (yes really). Recently moved to a new MacBook Air with latest OS (Sequoia 15.6.1).

Mac Mail - when I type the copyright symbol by itself © it automatically changes from the default 12pt size to a totally unwanted size 48pt.

This happens with ™ and some other symbol characters too. When I type two or three copyright symbols, they remain at 48pt. When I type four or more, they switch back to 12pt size.

What is controlling this behaviour??? I want to turn it off. It's so annoying. I cannot see the benefit or why it's being implemented.

It doesn't occur in Pages, Notes, Reminders or other apps or system apps. Just Mail (that I'm aware of so far).

I've tried:

1. Opening a new message, Edit > Substitutions and unchecking Text Replacement (didn't help)
2. Mail > Settings > Fonts & Colours > changing my default Message text and size (nope)
3. System Settings > Keyboard > Text Replacements (nope)
4. I will not change default mail format from Rich Text to plain text (thanks for suggesting in advance but no)
5. Checked System > Accessibility settings and can't find anything.

Help me Obi Wan Kenobis; you're my only hope.