Where a calm rule lands
Do not build a pyramid. Do not skip the thought either.
A host article that a few real readers share, or that your own newsletter points to, is a tier-two link in the wide sense, and nobody objects to it. The trouble starts when the second tier exists only to be a second tier.
If you decide to add links to a placed article anyway, point them from pages that would exist without your campaign. You choose the target URL on every order, so you can aim a placement at a host article you earlier placed, but the same judgement applies: relevance first, volume never.