[Lombra]

Should be fairly straightforward. Assuming you want to add the info to the game tooltip, you need to hook for example the OnTooltipSetItem script, parse all tooltip lines and edit the text accordingly.

Something like this:

GameTooltip:HookScript("OnTooltipSetItem", function(self)
	for i = 1, self:NumLines()
		local line = _G["GameTooltipTextLeft"..i]
		if line then
			local text = line:GetText()
			if textContainsRatingValues() then
				line:SetText("Replace text with this")
			end
		end
	end
end)