Publicize- and DoNotPublicize are entered as MsBuild Items. When used for things that are not actually files on disk, the IDE (Rider specifically) displays the Items in the project tree as broken files.

The below image has a project file with the following:

<ItemGroup>
	<Publicize Include="Assembly-CSharp" />
</ItemGroup>

The project builds fine, it's a purely visual annoyance.