Linux build ID 2000-041816 M16 in edit/preferences there used (untill recently) to be preference settings for how an enter or linefeed was to be treated. (options like <BR> <P> etc. were user tunable.) These settings are missing now. One consequence seems to be that when filing in forms (like bugzilla) - the "default" value of a <p> is used - which seems to translate to a double linefeed in forms? I seem to remember that when i set the preference to translate "enter" to <br>, i also got single linefeeds in forms. I don't know if this setting has been removed deliberately or is just temporarily missing while preferences are getting an overhaul, but found it worth mentioning.
those particular preferences were actually never hooked up to anything. At this time it doesn't look like we'll be able to complete the various ideas we had put in the preferences initially so we've removed them. If you are seeing a problem with form fields and double-linefeeds, please file a new bug. Thanks!
verified in 4/20 build.