<p>Maybe, but I'm not sure.  Note that my answer / suggestion to make it a synonym was well upvoted (+8) with no downvotes or dissenting comments for nearly two weeks before I went ahead with making the synonym.  You posted a dissenting comment yesterday, which now has 1 upvote, but it's not clear if it was before or after I made the synonym.  I do think it was reasonable to interpret the situation as a consensus for making the synonym at the time.  Of course, that doesn't guarantee a synonym is the best choice and we can always delete the mapping with little difficulty.  </p>

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<p>If I imagine a user who wants to ask a question here about the dummy variable trap, and who has (at best) a hazy grasp of the idea, I don't picture them trying to learn about it by mousing over the <a href="https://stats.stackexchange.com/questions/tagged/categorical-encoding" class="post-tag" title="show questions tagged &#39;categorical-encoding&#39;" rel="tag">categorical-encoding</a> tag.  Instead, I imagine them trying to ask a question.  I figure they would have some title with "dummy variable trap" in it, and would also type that in the tags field.  If someone were to do that under the status quo, they would see something like the following:  </p>

<p><a href="https://i.stack.imgur.com/ygtnT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ygtnT.png" alt="enter image description here"></a></p>

<p>That is, the similar questions section would show links to some relevant, existing threads, and the tag suggestions would include <code>[dummy-variable-trap]</code>, with it's appropriate excerpt.  (After they select <code>[dvt]</code> and post the question, <code>[dvt]</code> would be silently replaced by <code>[ce]</code>, but many people don't even notice that.)  </p>

<p>Alternatively, I might imagine such a user searching on the terms "dummy variable trap".  If I search on CV, I get <a href="https://stats.stackexchange.com/search?q=dummy%20variable%20trap">this</a>.  That is, the synonym didn't impair the search.  Searching Google is fine as well.  </p>

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<p>I think the issue is how the synonym affects searching on the tag (which I suspect primarily users more familiar with SE would do), and how having the mapping vs. not affects how well the information on the site is organized.  </p>

<p>I'm open to arguments on that issue.  In truth, I wasn't married to the idea of making the synonym beforehand.  But I continue to lean towards having the synonym&mdash;call it 60-40 for.  </p>
