The notion of "loopholes" rests on the idea that rules have a "spirit" (what they were ostensibly created to do) and a "letter" (how they are practically implemented). Finding a loophole is generally considered to be adhering to the letter of the law while breaking the spirit of the law.
In the examples you cite, the spirit of the rules is to promote a fun, balanced game. Making oneself invincible is considered a loophole because it results in an un-fun, unbalanced game. It's therefore against the spirit of the rules, even though it adheres to the letter.
What "spirit" would you be breaking if you suddenly discovered a way to drastically increase your own abilities?
What "spirit" would you be breaking if you suddenly discovered a way to drastically increase your own abilities?
That of envy avoidance- rising too high too quickly can also raise ire.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.