|This page in a nutshell: Guidelines should be followed, not ignored.|
Guidelines represent the thoughtful consensus of Wikipedia editors. Some, such as the Manual of Style, are essential for maintaining the uniformity and consistency that readers expect of a high-level publication. Although they do not have the full weight that policies do, it is important to follow guidelines as a rule. Exceptions to them should only be made when there is a compelling reason.
Often, editors become defensive of certain changes or styles present at a page they edit. When another editor comes along and makes changes to bring the article into accordance with one or more guidelines, the counter-argument presented is that such-and-such is "just a guideline" or "not a policy" and therefore should not be followed in this case. These editors are misapplying the notion that guidelines "should be treated with the occasional exception" while policies are considered inviolate. It does not follow that simply because exceptions can be made, they should always be made. Such logic would render guidelines impotent and remove all their value.
Exceptions to guidelines must be justified and logical. The burden is on the editors wishing to ignore the guideline to explain why it should not be applied rather than on those who wish to apply it. Those seeking to make an exception should be able to explain why their case differs from the situations that the guideline was created to address.
Also, some guidelines, such as those that govern how to capitalize section headings and subheadings, have very few, if any, exceptions. For instance, the "see also" section below is rendered in accordance with WP:MOS so as to have its first word capitalized and the rest of the words in lower case. There should be no reason that a functionally identical section in another article should capitalize both words, even though the Manual of Style "only" has guideline status.