Yes but that Tax Credit is paid for by the Levy - which is charged to all individuals who have health insurance. As I understand it the Levy is revenue neutral. Someone under 50 ends up being a net contributor to the Levy (as they get no corresponding tax credit to offset it), someone 50 - 60 ends up about even and someone 60 plus ends up being a net benefitor from the levy and therefore subsidised by others.
The whole point of community rating is to level the prices - which either requires the young over paying and the elderly under paying (via a levy type system) or requires a massive tax injection for the elderly (which means everyone in the country pays rather than just those on health insurance and would be regarded with those without insurance as unfair).
The only slight consideration here is that there are two levy rates depending if you have advanced or non-advanced cover. The idea presumably being that the (mostly younger, healthier) people on super cheap cover don't end up overly subsidising those (mostly elderly, sicker) on super expensive cover. But not sure it's enough of a difference/incentive to be honest.
However I'm not sure I buy Brendan's basic argument. Just because the younger are not getting as good a deal as the elderly does not mean you should opt out completely. It's like saying I pay more for my cinema ticket as I don't get a pensioners discount therefore I won't go see any films until I'm over 60.
Insurance is always an offsetting game and that's the point if it. Everyone who wants insurance puts some money in a pot and those that need to claim take the money out of that pot. You can argue the premiums you contribute should be risk rated, but ultimately, there's always winners and losers out if insurance. Should lucky people not buy insurance cause they are carrying unlucky people? Yes health insurance is less risk-weighted than other insurance, and yes younger, healthier people would get a cheaper price if it was allowed to be more fairly risk rated, and yes there might be better ways of deciding the levels, but that doesn't mean it's still not beneficial to have it in case the worst happens. Only when the premiums you pay in are greater than the claims you can make is the value argument so clear cut and, despite all the premium rises, we're not there (yet)!
Decide if cover is right (and affordable) for you and then get it at appropriate level of cover you want and can afford or don't get it if you feel it's of no value to you.