Hi,
I am not sure if I am missing a theme setting for this, or if it is a bug in the highlighting, but it appears that selections remove font styles like italics. I have comments set to be italic in my theme with
		<dict>
			<key>name</key>
			<string>Comment</string>
			<key>scope</key>
			<string>comment</string>
			<key>settings</key>
			<dict>
				<key>fontStyle</key>
				<string>italic</string>
				<key>foreground</key>
				<string>#586E75</string>
			</dict>
		</dict>
But when selecting text that contains a comment, the comment is rendered normal inside the selection highlight.
