Can an employer give more hours to people they like, and dock people they don't?

As long as he's not treating people differently because they're members of a protected class, he's okay. It's if he treats people differently because of race, gender, national origin, etc., that there are problems.

It's normal for an employer to treat people differently. You say it's for "personal reasons" and regardless of how someone does their job. However, you are not a mind reader. The employer readily may value loyalty, kindness, the ability to follow instructions, etc., beyond what you yourself see. The point is, you don't know what the employer says makes somebody good at their job. You have described no "personal reasons," such as if he's hired his little sister.

Anyway, no, you have not at all described "discrimination." Yes, the employer can treat people differently. If they have bad reasoning, they'll go out of business. You're free to seek other employment at any time.

They can run their business any way they like, within the local laws, provided they don't ask you to work at one agreed pay and fail to deliver that pay after you have worked. They can certainly offer to pay you less or give you less hours if they want to, and you get to decide whether you want to continue working there, under those conditions. Consider every day as a new "contract": you agree to go to work and they agree to pay you for that work. The day either of you no longer agrees is the day the employment is terminated.

You can reword your previous question any way you want, but the answer remains the same. You are not being disciminated against. You're a part-time employee, and the boss is holding this fact against you. It may not be tactful, but it's also not against the law.

Call corporate and a unidentified caller and tell them what you have seen not necessarily as an employee, maybe call as a parent, friend that you've noticed this and this happen on this many occasions. But call the corporate office.

Here in UK the people that get more shifts are known as the A*se Crawlers and yes they can do that and will find an excuse if someone complains, basically put up with it or find another job, Good Luck

Yes, they can.

They can treat people differently for ANY reason, except race, religion, gender, etc.

yes legal, no discrimination. Learn how to get along with people and you will get more hours

Of course and it is discrimination. The good kind. The kind of discrimination that elevates the hard working and conscientious and minimizes the damages from the detractors. It is not illegal.