Is the past perfect tense alien to Korean?

YES!

According to Lee Su-yeol (이수열), a native Korean who taught in Korean primary and secondary schools for forty-seven years, the past perfect tense (대과거) is not native to the Korean language; it was created to imitate the past perfect tense in English. Instead, Korean uses adverbs with the past tense to convey the meaning of past perfect. Therefore, the invented Korean versions of past perfect, such as -ㅆ던, -았(었)던, - 였던, -ㅆ었다, -았(었)었다, and -였었다, are all unnecessary.

I am going to use examples from a page on the "Korean Language Nerd" Web site, which promotes the Korean past perfect tense, to show that past perfect tense is not needed in Korean.

Korean Language Nerd wrote the following:

작년 한국에 왔어요 (past tense)
오다 (here as 왔어요) to come, implies to come to the place you are currently at, therefore the speaker came last year, probably stayed the whole time and is (still) in Korea. This translates to:
Last year (I) came to Korea.

작년 한국에 왔었어요 (past perfect tense)
Here 오다 (as past prefect tense 왔었어요) is a completed action, but since 오다 is used to express “to come here” the speaker must be at the moment in Korea, therefore it is implied the speaker came last year to Korea and left Korea again. This best translates to:
Last year (I) have visited Korea.

The Korean Language Nerd claims that 왔었어요 means that the speaker came to Korea, but is no longer in Korea. However, the way Koreans would normally express that meaning is "왔다 갔어요" or "갔다 왔어요," which is the way Korean was meant to be spoken and is much more easily understood.

Korean Language Nerd wrote the following:

추웠다. (past tense) It was cold and might be still.
추웠었다. (past perfect tense) It was cold but it isn’t any more. 

 This is silly. Do some Koreans really say 추웠었다? I cannot remember hearing it. You simply say 아침 추웠다; 어제 추웠다; 지난 겨울은 추웠다.

Korean Language Nerd wrote the following:

한국어를 공부 했다. (past tense) He studied Korean, and might be still studying.
한국어를 공부했었다. (past perfect tense) He studied Korean but he isn’t any more.

Why not 한국어를 공부한 적 있다 or 전에 한국어를 공부했다?

See! Why make Korean more difficult than it already is?

Finally, in my Dong-A 국어사전, the word "대과거," which is the Korean word for "past perfect," is defined as follows:

"(인도 유럽어 등에서) 과거에 있어서의 완료 (完了) 또는 계속을 나타내는 시제 (時制)"

The definition says "in Indo-European languages" (인도 유럽어 등에서); it does not say anything about the Korean language.

If you still do not believe me, read this 2003 중앙일보 article:

우리말 바루기 181 - 영어식 표현의 남용