Fonts, bold, colour and emphasis in Write by Zaweba
Character formatting in Write by Zaweba: fonts and sizes, bold, italic, underline, colour, highlight, superscript and the Font dialog.

A letter reads better when emphasis is used with a light hand. One bold phrase draws the eye; a page full of bold, colour and underlining tells the reader nothing is more important than anything else. Character formatting is how you set that balance, and Write by Zaweba gives you the usual set of controls without burying them in a ribbon.
What you can change
The font and its size are the starting point. Then come bold, italic, underline and strikethrough, text colour, highlight, and superscript and subscript. All of these work on the selected text, so pick out the words first and then choose what to apply.
The Font dialog brings the options together in one place. It is the best route when you want to change several things at once, such as font, size and colour for a line of contact details at the top of a letter.
Some extra effects have their own keyboard shortcuts rather than toolbar buttons: all caps, small caps and double underline. Help > Keyboard shortcuts lists them, along with the rest of Write's shortcuts.
Choosing the right kind of emphasis
Italics suit titles of books, films and publications, foreign words, and the gentle stress you would give a word when speaking. Bold is stronger. Keep it for things a reader must not miss, such as a deadline or a warning, or for the label at the start of a line in a list of terms.
Underlining is a hangover from the typewriter, when there was no other way to stress a word. On screen it can look like a link, so most documents read better with italics instead. Double underline still has a place under a total in a simple set of accounts.
Strikethrough is useful in shared lists and minutes, where you want to show something was dropped without removing it. Highlight works like a marker pen and is handy for marking text you need to come back to. Remember it prints, so clear it before the final copy.
Small caps make acronyms and short headings look refined, and all caps changes how letters appear without retyping them. Because all caps is a format rather than different letters, the underlying text stays as you typed it.
Superscript, subscript and colour
Superscript lifts characters above the line, which you need for things like squared units and ordinal endings, while subscript drops them below for chemical formulas. Select just the characters that should move, not the whole word.
Text colour is best used sparingly in documents that will be printed, because many people print in black and white. Dark blue or dark red reads well on paper and on screen. Pale colours that look fine on a bright monitor can almost vanish on a page.
When to reach for a style instead
Character formatting is direct formatting: it sits on the words you selected. That is right for one-off emphasis. For anything that repeats, such as every heading or every quotation, Write's styles are the better tool, because changing the style changes every place it is used.
If a document has picked up a muddle of fonts and sizes, Format > Clear formatting strips the direct formatting from a selection and lets the style show through again. The format painter, in the Edit menu, copies a look from one place to the next when you want two bits of text to match.
A sensible approach is to set fonts and sizes through styles, then use bold and italics by hand for the odd word that needs them. Your documents stay consistent, they convert cleanly when saved as .docx, and anyone you send them to sees the emphasis you intended.