Cleaning up messy text with Clear formatting in Write by Zaweba
Format > Clear formatting in Write by Zaweba strips direct formatting from a selection, so stray fonts and sizes give way to the document's styles.

Text pasted from emails and web pages often brings odd fonts and sizes with it. So do paragraphs copied from old documents, or a section someone else wrote and sent you. After a while a document can end up with half a dozen slightly different looks, and finding each stray setting by hand is slow. Clear formatting in Write by Zaweba sweeps it away in one step.
What it removes
Format > Clear formatting removes direct formatting from the selected text. Direct formatting is anything applied straight to the words or paragraphs rather than coming from a style: a font picked from the toolbar, a size typed in, bold, colour, a highlight, an indent dragged by hand.
What remains is the style the text is using. A body paragraph goes back to looking like every other body paragraph, and a heading goes back to its heading style. That is why Clear formatting works best in documents that use styles: the style is the clean state you return to.
When to use it
The most common case is a paste that came in wrong. If you forgot to use Paste as plain text from the Edit menu and a quote arrived in the wrong font, select it and clear the formatting. It will match the paragraph around it.
Another is a document that has been edited by several people. Each may have nudged spacing, picked a favourite font or added colour. Select the body of the document, clear the formatting, and then reapply the few bits of emphasis you actually want. Starting clean is often quicker than fixing things one at a time.
It is also handy when a style seems not to work. You change the font in a heading style but one heading refuses to follow. That heading almost certainly has direct formatting on top of the style. Clear it, and the heading picks up the style's look.
What to watch for
Clear formatting removes everything direct, including emphasis you meant to keep. Italic titles of books, a bold warning or a superscript in a measurement will all go back to plain text. Before clearing a long passage, skim it for formatting that matters, or clear a section at a time so you can see what you are losing.
Undo brings everything back if you clear too much. Undo in Write is unlimited, so even if you only notice later, you can step back.
It is also worth knowing that Clear formatting does not change the letters themselves. If text was typed in capitals, it stays in capitals. Change case in the Format menu is the tool for that job, and Shift+F3 cycles through its options.
A clean way of working
A good routine for any document built from several sources goes like this. Paste text in as plain text where you can. When something arrives formatted anyway, clear its formatting. Use styles for headings, body text and quotes, so changes are made once and apply everywhere. Add bold and italic by hand only where they mean something.
If you need two passages to look the same and they don't use a style, the format painter copies the look from one to the other. Between the painter, styles and Clear formatting, you can keep even a long, much edited document looking as though it was written in one sitting.
Clean formatting pays off when you save. A document with consistent styles converts neatly to .docx, exports to PDF without odd surprises, and looks the same when a colleague opens it in another program.