Note that this comment will only be shown for the "Congratulations!" string, and isn't very helpful in explaining how the string is used to localizers (they have no idea what page this shows up on, all they see is the string itself with a comment). Check out [Verbatim](https://localize.mozilla.org/fy/firefoxflicks/translate.html?unit=1153780) to get an idea of what a localizer sees.

I'd suggest changing this to "Congratulates the user on having an up-to-date version of Firefox." and removing the other one.