Since we’re seeing this over and over in answers here (and as an excuse in bug reports ) where should a “normal” user have received this recommandation ?
What link(s) can we share on this interesting hot topic ?
There is a value in learning and using styles efficiently. I guess, that this topic would receive some interesting discussion.
However, I want to emphasize, that an idea that direct formatting is purely wrong, and thus, any problems with using it are purely user’s fault, is not correct. The software must handle direct formatting just as well; and the only difference should be the natural topic of manageability of complex documents (use of direct formatting in them makes them unmanageable - just imagine an effort to change formatting of citations in a large text, where everything is direct-formatted, and the same formatting is used in different contexts), not their correct handling.
post title adapted
Direct formatting is nice for experimenting to see rapidly the result of such and such parameter.
When default configuration of styles does not fit tightly your taste (and I think this holds in 90% of circumstances), it is convenient to use direct formatting for one-shot dependable documents, e.g. a 1-page spot-on letter to an occasional provider.
As @mikekaganski points out, using styles instead of direct formatting is a matter of efficiency and maintainability. However you should not fall in “dogmatism”.
Styling is a way of "abstracting’ your document, defining various semantic categories for your paragraphs, words, pages, frames and lists. These categories must be broad enough to correctly describe the significance of the “objects” without detailing them uselessly. Taking the example of paragraph styles, built-in Heading n (and their related Contents n for TOC) and Body Text make the basis for all documents. You add to them a few “service” styles like Footnote, Header & Footer family, Block Quotation, depending on your topic, and you’re almost done. The subject of the document may suggest specific extra styles such as Comment, Example, Code Snippet, …
But if you end up with tens of user styles, then you have not correctly analysed the structure and purpose of your document. A correctly balanced style set should not exceed 15-20 effectively used styles in any category (except pages which could be more numerous and lists which are far less numerous).
This means that some “exceptional” circumstances should be treated as “accidents”. Instead of creating a dedicated style which will be seldom used, application of direct formatting solves “elegantly” this “accident”, e.g. a page break before some paragraph instead of a brand new paragraph style.
Also a lot of actions are not controlled by styles. They must be manually specified. They are usually related to text flow or non-typographical parameters. Among these, you have list tweaking like numbering reset or unnumbered item insertion.
As always, styling vs. direct formatting is a matter of personal judgement and acceptance of consequences. Styling offers more reliability and convenience and is practically mandatory on documents of more than 3 pages. There is nothing technically wrong with direct formatting but Writer has been designed around the concept of styles (and internally direct formatting is converted to one-shot styles, thus overcrowding the style dictionary). So the most efficient use is styling and direct formatting offers an easy entry level to Writer. But you should switch to styling in parallel with your skill improvement.
PS
Avoid mixing direct formatting with styling, at least when typographical attributes are concerned (font properties, paragraph geometry). You can create conflicting situations because both direct formatting and styles operate on the same attributes. If you understand the precedence rules, you’ll get your desired result. But you may easily forget that you have some direct formatting and be surprised later that a change in styles does not update the document appearance. Neglecting precedence rules is the dreaded formatting hell main cause.
Consequently, separate strictly typographical actions (where styles are at their best) from control flow and other actions (such as “exceptional” page break – but not one to switch to another page style, even if unique – or forcing list item numbering) where direct formatting has less nasty consequences.