user9943: It often happens that a quite ill-posed question uses tags that are relevant to the question, but that the answer(s) lead(s) to the question core, which is often a different field of Biology. 

Take Is addiction adaptive? as a quite random example case. The question is not neuroscience at all, likely because OP is not into that field. OP starts talking about feather pecking, which is, to my opinion, irrelevant to the question proper. Instead, I basically tried to tease out the question core and answer the relevant part, namely 'what is addiction'. This, however, is all about neuroscience. That tag was not included, likely because OP was expecting a more behavioral and evolutionary answer.

This is an example; it happens quite often that users dissect the question, take away incorrect assumptions, strip off the fluff and expose the question core. Then, my question is:
Should (preferably more experienced) users then decide to edit the tags?
Personally, I am hesitant to change the question proper, because there is a potential chance that OP did mean something different with the question. Additional tags, on the other hand, may draw in potential other answers without shifting question focus per se. 

user16651: As far as I understand the purpose of the Stack Exchange model, it is to provide expert answers, subject to peer review, to questions that could be of interest to a population greater than that of OP.
That being said, the users that have built up reputation by providing quality, expert answers, are the ones also given the keys to making and approving edits. 
As such, it is assumed that their knowledge and expertise in the subject matter is such that they are in the best position to assign questions to the tags that best reflect the questions and also the answers. 
Take, for example, HIV versus AIDS. Questions specifically related to AIDS are also relevant to HIV, as HIV is the virus that gives rise to the syndrome. However, and this may be entirely pedantic, a question about HIV does not necessarily need to be about AIDS. If someone asks "How does the AIDS virus integrate into people's cells?" I would say that should be edited to How does HIV infect a host cell and integrate into the host genome? Also if they tagged with aids, then I would say that tag should be removed and replaced with the hiv tag, as the virus does not necessarily lead to the syndrome (with proper antiretroviral treatment or very rare plasma membrane receptor mutations), and the virus' tropism isn't really a question related to the syndrome that it is capable of causing.
Tags are important as they target search. So if a quality answer is provided to a question, that may be of a different or broader scope than the original, because of the fact that you have a better understanding of the subject that the OP, then I think that it is perfectly valid to change or add to the tags, as the answer will likely be useful to people keyword searching on that subject.

9943: <p>It often happens that a quite ill-posed question uses tags that are relevant to the question, but that the answer(s) lead(s) to the question core, which is often a different field of Biology. </p>

<ul>
<li>Take <a href="https://biology.stackexchange.com/questions/41575/is-addiction-adaptive/41578#41578">Is addiction adaptive?</a> as a quite <em>random example case</em>. The question is not neuroscience at all, likely because OP is not into that field. OP starts talking about feather pecking, which is, to my opinion, irrelevant to the question proper. Instead, I basically tried to tease out the question core and answer the relevant part, namely 'what is addiction'. This, however, is all about neuroscience. That tag was not included, likely because OP was expecting a more behavioral and evolutionary answer.</li>
</ul>

<p>This is an <em>example</em>; it happens quite often that users dissect the question, take away incorrect assumptions, strip off the fluff and expose the question core. Then, my question is:</p>

<p><strong>Should (preferably more experienced) users then decide to edit the tags?</strong></p>

<p>Personally, I am hesitant to change the question proper, because there is a potential chance that OP did mean something different with the question. Additional tags, on the other hand, may draw in potential other answers without shifting question focus <em>per se</em>. </p>
 16651: <p>As far as I understand the purpose of the Stack Exchange model, it is to provide expert answers, subject to peer review, to questions that could be of interest to a population greater than that of OP.</p>

<p>That being said, the users that have built up reputation by providing quality, expert answers, are the ones also given the keys to making and approving edits. </p>

<p>As such, it is assumed that their knowledge and expertise in the subject matter is such that they are in the best position to assign questions to the tags that best reflect the questions and also the answers. </p>

<p>Take, for example, HIV versus AIDS. Questions specifically related to AIDS are also relevant to HIV, as HIV is the virus that gives rise to the syndrome. However, and this may be entirely pedantic, a question about HIV does not necessarily need to be about AIDS. If someone asks "How does the AIDS virus integrate into people's cells?" I would say that should be edited to How does HIV infect a host cell and integrate into the host genome? Also if they tagged with <a href="https://biology.stackexchange.com/questions/tagged/aids" class="post-tag" title="show questions tagged &#39;aids&#39;" rel="tag">aids</a>, then I would say that tag should be removed and replaced with the <a href="https://biology.stackexchange.com/questions/tagged/hiv" class="post-tag" title="show questions tagged &#39;hiv&#39;" rel="tag">hiv</a> tag, as the virus does not necessarily lead to the syndrome (with proper antiretroviral treatment or very rare plasma membrane receptor mutations), and the virus' tropism isn't really a question related to the syndrome that it is capable of causing.</p>

<p>Tags are important as they target search. So if a quality answer is provided to a question, that may be of a different or broader scope than the original, because of the fact that you have a better understanding of the subject that the OP, then I think that it is perfectly valid to change or add to the tags, as the answer will likely be useful to people keyword searching on that subject.</p>
