In the CLDR "x ago" are full strings. They will have a reason to have done that.
So, something like
* a moment ago * $1 {{PLURAL:$1|second|seconds}} ago * $1 {{PLURAL:$1|minute|minutes}} ago
and
Edited $1
with an approproate translators comment sounds best to me, and the time strings should definitely be in core and translated ony once across all of Mediawiki.
Maybe you can even take the "X ago" part directly from the CLDR?