<p><strong>I think tags should describe the contents of the question and nothing else.</strong> If our policy is that we treat textbook exercises differently (i.e. only provide &quot;helpful hints&quot;), then it makes sense to have a tag that is applied to questions posting textbook exercises. I think that's essentially that. If I see a question about PCA that does not have a [pca] tag, I add it. If I see a question that is <em>obviously</em> (!) a textbook exercise, why not adding the [self-study] tag.</p>
<p>In this thread @Glen_b and @gung (and @Tim?) argue otherwise. For the sake of discussion, I will now quote earlier statements that argue in favour of adding the [self-study] tag in obvious cases.</p>
<p>We had this discussion in 2012: <a href="https://stats.meta.stackexchange.com/questions/1172">Should we tag questions that smell like homework?</a> There @whuber wrote in an answer that has 17 upvotes:</p>
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<p>I think it's fine to retag (without comment) as long as it is perfectly clear that the problem is homework.</p>
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<p>We then had this discussion in 2014: <a href="https://stats.meta.stackexchange.com/questions/1904">Is it okay to add the [self-study] tag through an edit instead of asking OP to do it?</a> There are no answers, but most upvoted (9 and 8) are two @gung's comments (note that @gung wrote has changed his opinion since then, see his answer &amp; comments):</p>
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<p>I don't have a problem w/ people editing questions to add the [self-study] tag, &amp; I do it myself. This is especially true when, as here, someone just copies &amp; pastes a question from their homework. [...]</p>
<p>Regarding the issue of politeness, you raise a good point. When I edit to add the tag, I always also leave a comment (which I just copy &amp; paste &amp; change the name). [...]</p>
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<p>@NickCox agreed:</p>
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<p>Always asking first would be polite, but I don't think it is especially practical. Often these questions come from new or inexperienced users not familiar with tagging, or much else; indeed they often back off and disappear when people don't do as they ask. Removing a mistaken tag is easy and painless when needed.</p>
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