Stats past maximum.

I realize this is kind of a dumb question, but does raising your stats past their maximum do any good. For example.

Dex: 23(23)^2

Is my dex effectively 25? Or is it just 23 and I'm wasting a piece of equipment that is increasing my dex by two?

I don't think I am giving away any secret info...or at least I hope not...but I think it would be useful to have a stat raised above max just in case you go against a foe that can give some of those stat's negatives...so, having a plus 3 to str...then, having some spell cast on you that causes you to lose 5 str...well, you would only be at a loss of 2...which would be far better than the full 5

Some items also make you lose stats, so you can counter the loss with other items by utilizing this.

Yup. That's right.

I may be biased but I listen to the professor. But All the above is good advice.

To officially answer the question your dex is not effectively 25, for the dynamic of AC/dodge, but it is effectively 25 with dynamic to penalties acrued due to negative spells, as the professor explained.

Some mal's also reduce certain stats.

It is good to have a +# on things like STR to counter these.

That is why you strike DEX first and don't bother with STR unless you can stack penalties above -5.