There’s a problem with how text selection interacts with HTML tags in the Add window.
I’ve recorded a video to show it here: Video Link
Version <U+2068>2.1.65 (aa9a734f)<U+2069>
Python 3.9.15 Qt 6.4.3 PyQt 6.4.0
(Side note: the Anki version info includes some invisible Unicode characters that show up when copied and pasted into the forum, as seen above).