Well, if you leave the HTML tags in question outside the strings and only localize the sections that do not give any problems.
For instance, replace inside settings.xul
and remove the last bit from the localized string.
Mind you, I am not a coder at all, so others might be able to provide better advice than me on this matter. Not able to help at all on the %s, all I know is that it can be used, but I don’t have a clue how.
I don't think that hardcoding <br> in settings.xul will work for all languages. I mean, <br> may be the last word of pref_rep_br.cap
in English, Dutch and Portuguese, but it may come before in German and Japanese, for example.
English : pref_rep_br.cap = "NOTE: Will not replace new-line which following an HTML tag with <br>
German : pref_rep_br.cap = "HINWEIS: Es wird keine Leerstelle innerhalb des HTML Tag mit <br>
Japanese : pref_rep_br.cap = "注：HTMLタグに続く改行は<br>