Repeated text - in general and for security

Hi!

english/lts/security/index.wml and english/security/dsa.wml has a block of
repeated text as the comment in lts/security/index.wml clearly states.

How do we properly fix this - here and in general? In Norwegian, I have
created _sub_some_topic.data (with the common text) and included them where
relevant. Is this the proper webml way? Does it break translation stats or
other tooling?

Hans