WordPress created a non-removable Tweet-button after copying text from 2 emails

[hero2]

Hi

I created a new Post for my blog by copying the content of 2 emails from Thunderbird v.115.6.0 into a blank Post. None of these emails contains anything remotely resembling a Tweet-button, but the resulting Post has a Tweet-button in the lower right corner of the Post. And this button cannot be removed...! At least I cannot see any way of removing it.
This is really a weird bug! It confirms to me how fundamentally hopeless and flawed WordPress is...
You can see the Tweet-button here:
​https://www.transformation.dk/interessant-dokumentarfilm-om-alternative-kraeftbehandlinger/

The "Component: Editor" field below mentions the Gutenberg Editor. I don't know if my WordPress installation uses Gutenberg. It uses the wpastra.com theme (including Spectra).

I have attached a document containing the 2 clipboard clips of Thunderbird emails, that I inserted in the WordPress Post editor, resulting in the creation of a non-removable ”Tweet”-button in the lower right corner.

[hero2]

These are the 2 clips of emails that resulted in a non-removable "Tweet"-button

[swissspidy]

Hi there and welcome to WordPress Trac!

For help with issues specific to your site, we usually recommend asking in the ​support forums to get assistance.

In this particular case, you appear to be using a blockquote block from the "Ultimate Addons for Gutenberg" plugin, or better known as ​Spectra. So yes, you appear to be using Gutenberg. If you want to remove the Tweet button in Spectra's blockquote block, please ask in ​that plugin's support forums for help.

I'm closing this issue because it's not a bug in WordPress itself, but related to a third-party plugin.