Never odd or even

• I can be long or short and most people can appreciate me.
• But not everyone can easily create me.
• If I see you mirrored, you are me.
• But if I see myself mirrored, I am not.

What am I?

• How Can Mirrors Be Real If Our Eyes Aren't Real – Romain Fournereau Jul 26 '16 at 10:01

Are you

A palindrome

I can be long or short and most people can appreciate me.

Palindromes can be short ("Madam, I'm Adam") or longer ("A man, a plan, a canal: Panama!") and people generally appreciate the cleverness, not least because...

not everyone can easily create me.

If I see you mirrored, you are me.

If you look at me and see me mirrored, I must be the same as myself mirrored

But if I see myself mirrored, I am not.

If I can look at myself and tell that I am mirrored, then I must not be the same as my mirror image.

Finally,

The title of the puzzle is a palindrome

• Ha, nice, I completely forgot about the last part (of your answer)! I think this might be it. – bg6471 Jul 25 '16 at 11:14
• Good work! Correct. But see my answer for some explanation on how I meant it. (I couldn't place comments with spoilers here.) – nl-x Jul 25 '16 at 11:26
• Knowing songs from Weird Al Yankovic, I knew answer before I read the question. – Zikato Jul 25 '16 at 12:40
• I don't understand the mirrored part at all... – Devsman Jul 25 '16 at 16:33

long or short

shadow can be long or short

But not everyone can easily create me

Mirror

shadow in mirror does not create actual image of us.

• Ooh. That's a nice one. But no, that's not it. – nl-x Jul 25 '16 at 9:41

See the answer of @aPaulT , which is correct. But a part of his explanation isn't how I intended it:

If I see you mirrored, you are me.

Since I am a palindrome, If I can look at you mirrored and still see you, then you are a palindrome (thus me).

But if I see myself mirrored, I am not.

Because if you mirror palindrome, you get emordnilap. So I, palindrome, am not a palindrome, thus I am not myself.

• My first guess was ton: There's a short ton and a long ton and when mirrored it reads "not". I culdn't make that guess fit with the rest of the clues, of course. – M Oehm Jul 25 '16 at 12:14
• Are you by any chance familiar with Weird Al Yankovic's "Bob"? – supercat Jul 25 '16 at 16:04

Reflection

I can be long or short and most people can appreciate me.

Depending on the height of the person, or convex/concave mirror. Most people can appreciate their own reflection

But not everyone can easily create me.

Not everyone can easily create a reflection, due to surface maybe?

If I see you mirrored, you are me.

If the reflection sees you mirrored, then you are the same as the reflection

But if I see myself mirrored, I am not.

If the reflection sees itself mirrored, then is not the same as the reflection (following from the line above, "you are me" to "I am not [me]" - ie. from the point of view of the reflection, it's own reflection is not the same as itself - it's mirrored)

• Also not what I was looking for. Plus I don't follow what you say in your last line. – nl-x Jul 25 '16 at 9:55
• @nl-x I just edited to try to explain a bit better – bg6471 Jul 25 '16 at 10:04

Sounds vague, but are you:

A biography

I can be long or short and most people can appreciate me.

Biographies can be long or short

But not everyone can easily create me.

It is not easy to write one.

If I see you mirrored, you are me.

I am a biography if I am about you (for example).

But if I see myself mirrored, I am not.

But if I am about the writer, then I am not a biography. I would be an autobiography then.

• No price for you either :) – nl-x Jul 25 '16 at 10:16