A line and font has changed

When I hit enter in Libreoffice Writer to start a new paragraph, a line appears and my original font color has changed and is underlined. How did this happen and what should I do? Thanks in advance!

I figured it out.

Perhaps for the benefit of others who may experience the problem you could edit your answer to explain your solution.

I’d guess it is related to tracking changes.

Likid has the correct answer.