<p>What's at stake here?</p>
<p>OP has doubt regarding the veracity of an answer to a question that has been closed.</p>
<p>Now OP needs clarification. What could be done?</p>
<p><span class="math-container">$\bullet$</span> <strong>Comment!</strong> Seriously, leave a comment to the post seeking clarification re OP's concern. The poster, if needed, would surely respond or(and) might edit the post, if necessary.</p>
<p><span class="math-container">$\bullet$</span> If the user is no more in the site, then still leave a comment behind, for there could be others who could notice and respond to that.</p>
<p><span class="math-container">$\bullet$</span> <strong>Ask a follow-up question.</strong> Explain the concern in a new question re any assertion made in the answer to the previous question. But make sure to explicitly reason as to why it's not a duplicate. That is, it is to be asked with clarity why, at the very first place, the concern is legit and that warrants a different post.</p>
<p><span class="math-container">$\bullet$</span> Also, one thing to be noted is to why the original question was closed: it was marked duplicate. So, one can resort to that question for more info.</p>
<p>Finally, one more I would like to add is that if a post is wrong or disseminating misleading assertions, chances are there would be responses from the community: it's highly likely the errs don't remain overlooked from the vigil eyes, if there is any error at the first place.</p>
<hr />
<p>TL;DR: Interact with the poster airing the concern primarily by resorting to comment.</p>
<p>Some related posts across our sister sites in the same vein:</p>
<p><a href="https://meta.stackexchange.com/questions/128449/how-to-ask-for-clarification-of-an-answer">How to ask for clarification of an answer? </a></p>
<p><a href="https://meta.stackexchange.com/questions/110216/what-should-i-do-if-i-want-more-clarifications-about-an-answer-posted-on-an-old">What should I do if I want more clarifications about an answer posted on an old question?</a></p>
<p><a href="https://math.meta.stackexchange.com/questions/4108/clarify-an-old-answer">Clarify an old answer</a></p>
<p><a href="https://physics.meta.stackexchange.com/questions/14154/how-to-ask-for-clarification-on-a-very-old-answer">How to ask for clarification on a very old answer</a></p>
