When adding comments to a Sales Order, and using Enter to add a line break, those line breaks are not respected when redisplaying the comment after the comment is saved. However, the line breaks are saved, because editing a comment shows the correct line breaks.
Please replace linebreaks (\n) with <br/> tags, or wrap text in <pre> tags when redisplaying to ensure line breaks are preserved. A WYSIWYG editor for comments would also be handy, but definitely non-essential.
The same applies to comments in POs.