I try to reproduce your issues, but cannot succeed
The first issue:
2. Open Notepad
3. Input "this is a test" in Notepad
5. Place the cursor directly ahead of "this is a test" and then press "Enter", one new line will be generated and the cursor is still in the first character of this new line. It is correct.
The second issue:
2. Input "This is a test"
3. click button "Bold"
4. Place cursor directly ahead of "This is a test", and then press Enter
The strong tag is not removed.
Can you test it more and tell us which steps are different from yours?
Regards,
Eric