It actually lies somewhere in the middle.
Catholic Liturgical Laws say “Do this. Do exactly this.”
Liturgical Laws don’t operate the same way civil laws operate—where they either prohibit something (like burglary) or they require something (like a license to operate a restaurant).
It is a misunderstanding of liturgical laws to say “if it’s not forbidden it’s allowed.” Liturgical laws say “this is how it’s done. Do it this way.”
The maniple was never suppressed. However, it is not described in the Roman Missal anywhere. Therefore it is no longer a part of the vestments. It was simply omitted (intentionally) from the description of the vestments in the Missal.
Wearing one does not have any actual impact on the vestments–in other words, this is not like wearing an overcoat on top of the chasuble, or wearing a secular hat on ones head. It is similar (though I’m not saying equivalent) to a priest carrying a handkerchief in case he sneezes or wearing a sweater beneath the alb if it’s cold.
I wear one sometimes, but very rarely.