<p><sub>A search of type <code>[edits][title]</code> on Meta Stack Exchange and Stack Overflow Meta did not help much.</sub></p>

<p>My two cents. I'd say we should be cautions to edit a title to encompass (all) existing answers. The recent <a href="https://stats.stackexchange.com/questions/128616/whats-a-real-world-example-of-overfitting">overfitting</a> question asked for real world examples and it collected answers out of this scope. Not sure if the title should be edited in that occasion.</p>

<p>On the other hand, editing the question's example seems perfectly fine. </p>

<ul>
<li>the OP mentioned PCA in the question body.</li>
<li>the answerer of that question tagged it with <a href="https://stats.stackexchange.com/questions/tagged/pca" class="post-tag" title="show questions tagged &#39;pca&#39;" rel="tag">pca</a>.</li>
</ul>

<p>You would be adapting/improving the title to what already exists in the question as a matter of content.</p>
