For the Roman Catholic, though not the Christian, that's a mortal sin.
Now, I have been able to show where an officially approved version of the Bible for Roman Catholics (NABRE) has been shown to insert words to the text of Matthew 19:9. It is the only English version to render the passage in this manner.
I even posted an article from Msgr Pope where he made the claim the verse supported the insertion by the Greek. I showed the verse in question in Greek and demonstrated the Msgr's claim is false.
So, no. The insertion of the phrase, unless the marriage is unlawful, is not part of the Greek and is not supported by the text.
It may be authorized by Rome but that doesn't make it right.
There is a difference.
Prior to the age of the internet Roman Catholics might get away with such claims in discussions. No longer though.
Therein lies your mistake. That's the way "authority" works.
Furthermore, comparing a helpful, authoritative, clarifying addition to one whose only purpose is to promote a heretical doctrine no one ever heard of for 1500 years is hardly apt.
When will Protestants get it through their heads Catholics pointing out Protestants don't practice their own principles does not obligate Catholics to practice Protestant principles?