It contains the text "Toggle the table of contents" and if you copy the title of the page you may accidentally also copy this text.

Steps to replicate the issue (include links if applicable):

• Go to an article on Wikipedia, for example open the article Wikipedia
• Select the title Wikipedia but extend the selection area to include this image
• Do a copy action to save that in clipboard
• Now Paste the clipboard in a text area

What happens?:
Wrong clipboard is saved because it would be : "Toggle the table of contents Wikipedia"

That is, the first segment (i.e., "Toggle the table of contents ") makes the clipboard wrong.

What should have happened instead?:
We should make the ToC unselectable. This way, only the title of the article is selected in clipboard.

Software version :
Vector 2022 in Wikipedia

Other information :
One possible solution could be applying this style:

.vector-page-titlebar-toc {
  -webkit-user-select: none; /* Safari */
  -ms-user-select: none; /* IE 10 and IE 11 */
  user-select: none; /* Standard syntax */
}

I have tested this style in my css page and it works well.