show placeholder text and value in source locale in translated forms for fields not in the source locale.
add some missing translations.
thread header only needs to re-render when there are changes to the thread title or summary.
add lang-switcher event handler on thread header modal.
use empty string for default placeholder.
add class name to comment form in submit comment link modal so we can trim the margin off the bottom.
don't show placeholder if source locale is not set.
migrate logic for changing translatable field labels in form when locale changes to translatable form itself.