See there a real mix of reasons to re level, some more logical then others, now this is just my opinion but I feel it comes down to streamlining a character to what you first envisioned is fair, Iv messed up countless times on level up to feats and skill points. (even with mapped out spreadsheets of what I wanted)
A good example was animal handling, I put 1 point into it because it has a use at lower levels and with equipment boosting it. but once I have a dominate animal spell, animal handling point was just dead (little point in animal handling rats when you can have tigers). So its just not logical to keep that point there. - now i feel this should be fine in my opinion to re-use that point, as long as i keep that spell because in RP sense its the same and logically better chance with the spell and not fundamentally change the RP with it (ie putting it in tumbles or disaplin but not say ride).
now, removing the spell could be abuse because iv lost an RP aspect that my charecter could do?
If i put that point into lore and now able to use the scroll is that a grey area?
This is when it comes into question. Abuse or not?
While on the other hand I feel like wildly changing on a re-level is terrible and should be punished, epsically if you have established yourself in a lot of RP that then you cannot do that RP later on because of the re-level.
It's where that pcc server comes in I guess, to map out them levels correctly to limit such from happening. But I also feel like the changes in the game will make many people re-level anyway. I know of at least a person who had a viable build that changed so it wasn't and re-leveled trying to keep the spirit of the character but sadly fundamentally was different.
But at that point I feel it makes it unfair to be classed as abuse.