Hi all, first of all, I would really appreciate changing the thread title. "So broken" is not really true.
The current behavior of bump/normal map filtering is expected in Corona. We do however have some user reports where it is clearly not optimal, so we will do our best to improve it in future versions. On the other hand, we are not getting many reports like this, so it can't be that bad. ;)
There are some reasons for bump filtering, for example imagine that you have an object with strong, sharp bump far away from the camera and you animate it (either the object or the camera). You would like to see smooth movement, but with low or no filtering you will see strong high-frequency flickering of the bump map. Filtering "blurs" the texture so the result will be more acceptable.
You can negate that kind of high-frequency flickering, for example with output clamping (which AFAIK - I may be wrong - happens in fstorm by default), but we do not want it as we always choose rendering quality over heavy bias.
There are also some other fixes/improvements possible to implement in Corona, but they will require a lot of research and development from us.
If you have some examples where the current behavior fails, please send them over - we are always happy to investigate, offer some workarounds, and log specific cases for our devs to review.