Putting a word in boldface is even more offensive than writing it in ALL CAPS. If you are doing it more than once per year, you are doing it wrong.
But for technical communication where you're using names of things that have a controlled vocabulary, it's really helpful to put those words in a bold mono-space font. Otherwise, you end up using quotes too much and that gets tiresome.
I said this as a personal opinion; no idea how widespread that is. Boldface strikes me as a lack of respect for the reader. An adult reader is supposed to read the whole text. If there is non-important information, please omit it.
The idea if writing a short sentence at the beginning summarizing the action to take is sound, however. It is even better if it appears in the subject of the message.
I wish to work in the utopia that is your office if this is even slightly true in practice.
I tend to emphasize not a lot in emails where a reader that's skimming might skip the not and get the opposite of the impression that I intended.
Yeah, that's bullshit. Open any CS book on your shelf and you'll see different fonts, different sizes, different weights, different background colors, etc. Those books are not written for kids, they're written for adults—for professionals. The goal of a writer is to control the reading process; changing what the text looks like is one way to do that.
We separate the text into paragraphs to delineate different ideas, but also to space out the text and give the reader a chance to breathe. We organize points into bullet points because they're easy to spot, easy to scan, and we don't need to make the text longer by adding flow between each point. We sometimes use frames and a darker background for summaries, auxiliary information, etc. to show that it's not part of the main text. We use large letters to identify different chapters and sections. We use a monospaced font for code examples. We write technical terms in italics when we first introduce them and want to highlight that fact to the reader.
There are a multitude of ways in which we format text so that readers can better follow. Bold is just one extra tool in that arsenal. Don't abuse it, but don't forbid it entirely either.