Can a corrupted gem still be able to level up?

So I vaal'd my lvl 20 gems, one of them was down to lvl 19 so is it RIP or ?

You are in a unique position to try it out for science :)

To be honest, I feared to corrupt my 20 lvl gems just because I did not know the answer (I still don't know it) so please try it out and let me know

yup it is gaining exp but not sure yet, gotta wait it out I guess :-)

Corrupted gems still get experience, but lost quality is a horrible prospect.

I've lost a level or two to corrupted gems. I would never use it on a lvl'd gem, dats some yolo stuff right there. I would always do it at a lower lvl, because if you do get screwed you can lvl back really easily, and if you get a gain, well, you win.

doest the +1 level effect change only current level or max level aswell ? can you for example corrupt lvl 1 empower to level 2 and then level it up to lvl 4 ? or lvl 3 will still be the maximum lvl ?

The bonus level only adds to the level, not the max level. You'd have to max out the gem first for it to go above the maximum gem level. If you lose levels by corrupting a gem, you will have to level it again, but you did not occur any permanent penalty past not being able to alter the gem again.