Arco and pizz. text should be non-italics
- Arco and pizz. should use the "Staff" text style and not the "Expression" style.
- The same applies to all channel-change text, such as "tremolo", "mute" and "open".
It is always good to provide a source. Mine is p.492 of Elaine Gould's "Behind Bars", where she explains which styles are used for which kinds of text. The key point is that there is a distinction between "technical instructions" and "expression markings". My understanding is as follows:
Technical instructions refer to methods of playing an instrument, such as plucking or bowing, and are usually specific to certain instruments. These are displayed in a roman (non-italic) typeface, which means using the "Staff" text style in MuseScore.
Expression markings refer to styles (e.g. staccato/legato) or emotions (e.g. brightly/sweetly) of playing. These are usually generic to all (or nearly all) instruments. These are shown in italics, which means using the "Expression" text style in MuseScore.
This should be easy to fix. The change needs to be made in the Master Palette and Basic and Advanced workspaces. The workspaces are just zip files with XML inside, but you need to double-check that MuseScore can actually read the ZIP file after you have edited it.