src/vs/base/browser/formattedTextRenderer.ts/formatTagType
function formatTagType(char: string, supportCodeSegments: boolean): FormatType {
	switch (char) {
		case '*':
			return FormatType.Bold;
		case '_':
			return FormatType.Italics;
		case '[':
			return FormatType.Action;
		case ']':
			return FormatType.ActionClose;
		case '`':
			return supportCodeSegments ? FormatType.Code : FormatType.Invalid;
		default:
			return FormatType.Invalid;
	}
}