User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:94.0) Gecko/20100101 Firefox/94.0

Steps to reproduce:

1. Open Thunderbird
2. Type mail title eg. "test 123"
3. Mark text title "test 123" and try move marked text to message window

Actual results:

1. Marked text "test 123" not moved
2. Blinking Cursor stayed in this place where I try move "test 123"
3. When I try type text in different place on message cursor blinking, blinked cursor stay in this place where I tryed move "test 123"

Expected results:

1. Marked title text "test 123" move to message window
2. I see blinking cursor in this place where I actually writing message, not in this place where I tried move title text

Dragging text from subject to message body works for me when using beta 96.
I would not necessarily expect the cursor to be placed at the pasted text.

I would guess this was fixed in 91.4.0 via bug