It's totally fine to bump them if you do so in a relevant and appropriate way and the thread can still be useful to other members 
With regard to paying upfront and getting the discount or not, my personal stance is as such. Keeping the $500 for now when I'm a poor uni student and then paying it back later when I'm (hopefully) employed full-time is I reckon more valuable than paying $450 now which is less than I'd have paid otherwise, but I don't have the money to put towards extra-curriculars, textbooks, uni life, etc.
And really with interest it's far more valuable to put the $500 in the bank. Over the course of ten years with a 4% interest rate (a bit generous but #) $500 becomes $740 (compounded per annum). So after paying back your HECS you now have $190 more than if you'd given up the money 10 years ago to save $50.
didn'taccountforinflationsrsynotsry
Interest rates for normal savings accounts are usually only a half percent higher than inflation, but I still agree with your point. You're not really going to make a profit out of it, but I agree that as a uni student that money is more valuable to you now compared to once you'll be working full time.
Inflation rate government loan is the best loan you're ever going to get. Gearing ftw.