Pressing enter at end of text at end of comment does not continue to move cursor down - UI does not show cursor as where it actually is (typing letters corrects this).
Create a new comment, type a sentence, then press enter (ie return) - once, twice, three times. Observe where the cursor is.
Then type and watch the text/cursor jump down to where there was no text previously.
reproducible on multiple releases up to old 3.3.3.
bug is present in AOO 4.0.0 as well, so I suspect it's inherited from LibO.
it affect just Writer comments. Calc comments are unaffected.
as said by reporter bug is evident only after hitting "enter" more than 3 times.
tested under Win7 64bit
*** This bug has been marked as a duplicate of bug 41833 ***