I finally found out markdown has a way to add linebreak instead of just paragraph break. Sounds obvious in retrospect to look it up, but it just never occured.

1 this is a line breakd sentence\
2 this is a sentence after line break
3 this is a sentence with no prior line break

4 this is a sentence with paragraph break

and this renders as

1 this is a line breakd sentence
2 this is a sentence after line break 3 this is a sentence with no prior line break

4 this is a sentence with paragraph break