If I ask someone, what is a piece of clothing is, that this personey would never wear, m? Many would take a moment to think about it.

Commas (,) tend to be used to separate different thoughts or ideas. In this case, the way you wrote your sentence sound like you wanted to ask 2 different questions. "what is a piece of clothing?" and "[what is clothing] that this person would never wear". Since these 2 ideas are related, you want to connect them without a comma (,).

Then, they would listing items of clothing, that they percieive as unflattering, and ugly.

I don't have a good explanation of why not to use "listing" instead of "list" here, other than it sounds "incorrect".
Additionally, the use of commas (,) is used to sperate different ideas. Since the "perception of unflattering and ugly" applies directly to the "clothing" that the "person is listing", they should not be separated with commas (,).

TSuch as, things, that once werwere once worn by many people around the world, because they were considered pretty, and trendy at the time.

"Such as" is not absolutely necessary to make this sentence correct, but it makes it flow better from the previous sentence.

That, whatich was once considered cool, is now uncool.

"what" is still correct, but "which" sounds slightly better.

However, I would takhave a different take on this question.

"take" is still correct, but it sounds slightly better to not use the same word twice. Some alternate sentences could be.
"However, I would answer this question differently."
"However, I have a different take."

If you wouldere to wander the streets, and would ask a random person what they think about skinny jeans, it is likely that the answer will often times be the same.

"would" is technically correct, but sounds unnatural in this sentence.
Adding the second "would" is a little redundant, because you established the tense (past-tense in this case) with the first "would" ("were to" with my suggestion).

I don't believe that anything is necesseralarily ugly.

There are people out there, who can wear them and look absolutely stunning.

Also, I don't wear them, not because I think that they are ugly, I don't wear thembut because I have fat legs, and don't want to highlight them.

Your sentence was fairly good as is, but it was a little redundant to say "I don't wear them". Since you already said that you "don't wear them" at the beginning of the sentence, it is assumed that that is the case throughout the rest of the sentence.

This is why I never wore them, even while they were trendy (Yes, I was a child.,

It makes more sense to end "I was a child" with a comma (,) rather than a period (.) since you continue to give more detail to that statement ("I was a really self-conscious child").

Yes, I was a really self-conscious child).

This correction only makes sense with the correction above, about replacing the period (.) with a comma (,). Since the "Yes, I was" become repetitive with that change.

Still, I don't judge people for what they are wearing, and I would never say that a piece of clothing is ugly.

This is a great use of a comma (,) between "wearing" and "and I would". Since "I don't judge people for what they are wearing" and "I would never say that a piece of clothing is ugly" are different thoughts, this is an correct use of a comma (,). Great job!

If I ask someone, what a piece of clothing is, that this person would never wear, many would take a moment to think about it.

Then, they would listing the items of clothing, that they percieive as unflattering, and ugly.

Things, that once were worn by many people around the world, because they were considered pretty, and trendy at the time.

That, wWhat was once considered cool is now uncool.

If you would wander the streets, and would ask a random person what they think about skinny jeans, it is likely that the answer will often times be the same.

I don't believe that anything is necesseralarily ugly.

This is why I never wore them, even while they were trendy (Yes, I was a child).

Yes, I was a really self-conscious child).