We would not recommend this. LinkedIn as a platform is for connecting with individuals, getting in touch with professionals and experts and interacting with them. Mostly we have observed people using LinkedIn groups to promote their business. This is strict NO. Discussion Groups, as the name itself says, are for discussions. Use them to discuss interesting topics, share point of views and learn. Don’t dilute the purpose by commenting with product promotions. Do it ONLY IF you truly believe that your product offers the value in line with the discussion which is going on.