Tempo text font

MS follows Gould rules. Tempo text is written above staff in bold.
If you want to change the default behavior, you can change the style.
Format => Style.
-Tempo text
-Text styles => tempo.

I agree that there are publishers that do use, for instance, bold/non-italic text for the movement start tempo indication, but then (usually non-bold) italic text for at least some following tempo indications such as ritardandos and the like. But it's only the Gradual Tempo Change elements (rit. - - - - etc.) that you currently can't modify the text formatting properties for on a per-element basis - you can only edit the "Gradual Tempo Change" style for the whole score. You can also use "System text lines" (there's one on the Palette that shows as "System ---┐"), which won't affect playback, but you can choose a different font for all of those (actually it will affect all text line elements). For any tempo indications that don't need a line, you can edit each element independently (and create your own palette entries etc.) - certainly for "a tempo" that's not an issue (just select the element then use the properties pane).
Possibly worth a feature request to allowing overriding text formatting properties for "gradual tempo changes" and "text lines" on a per-element basis?