First thing to do is check their profile to see if they have any preferences about being contacted (or not contacted).

If they have a link to a personal website in the profile, it's worth clicking on that and seeing if it has a contact page.

If there's nothing about this in their profiles and they don't have a contact page, you can try sending a private message by using the mention-only post.

FWIW the impersonating accounts I've seen a couple dozen or so of are all impersonating folks not using their account, and I think they also block the accounts they are impersonating so it's difficult for anyone but a third party who knows about the authentic account to notice

In general, however active your account is, if there's someone impersonating you, report it to your own server admin and to the admin of the server where the impersonator is. If the remote server refuses to take action, your own admin may choose to restrict or block the remote server.

You can hide your account's follow and follower lists to prevent anyone copying them (more info: https://fedi.tips/how-to-hide-your-follows-and-followers-in-mastodon ).

Deletion would make it harder to prove you're being impersonated or cloned.

Do you mean posts by different people which link to the same news article?

Probably best would be using Mastodon's Filters feature, more info at https://fedi.tips/filtering-your-timeline-to-hide-posts-on-mastodon

You can use this to set up a filter for the link to the article.