While I can’t offer much on the login issue, which works for me in Safari, I wonder if the line break issue is also tied to your browser(s), and not a generic issue. Might the Mozilla engine be sending different codes for ‘P’ or ‘BR’ than do other browsers, with the accompanying mis-interpretation by this interface?
Most of the posts in the Neighbourhood show paragraph breaks, though I’ll state that on most occasions, the automatic capitalization of new paragraphs on my iPad does not work as expected, so work is needed.
@telusfeedback - It appears to be an issue with the way Firefox is processing the script. If you hit Enter a second time after entering your login details, it will log you in to My Account. Tested on Firefox 43 and 61.0.1. Both have the same behaviour.