Only Namu Myoho renge kyo is correct because Namu Myoho renge kyo is the personal name of the Supreme Law. Neither Namo Miao Fa Lien Hua Ching, NamasSaddharmapundarikasutra nor Devotion to the Scripture of the Lotus Blossom of the Wonderful Dharma is the name of the Supreme Law.
To take this one step further, not even Nam Myoho renge kyo is the name of the Supreme Law or Nichiren would have written it as such.
Mark, you're ignorance of the Japanese written language is complete.
For others who are interested, the Japanese written language incorporates Chinese characters. In some cases, the Chinese characters are pronounced in a way that is derived, but different from, a Chinese pronunciation circa 800 CE. In other instances, they are read with wholly Japanese readings. It would be like adopting the Chinese character for dog, 犬, to write "dog" in English.
In reading, there are often cases where two characters read together are contracted. For instance, this is the character for Buddha: 仏 (the modern, simplified version) read as butsu
or alternatively, hotoke
, the former being a transliteration of "Buddha" via Chinese, and the latter being the Japanese word for Buddha. This is the character for teaching: 教 read as "kyo" or alternatively "oshie", the former being derived from the Chinese and the latter being the Japanese root for "teach". When read together 仏教, we don't read it butsukyo
, which would not be incorrect, but its read bukkyo
, and literally means, Buddha's Teachings, and is used to refer to what we know in English as Buddhism. The reason for the contraction is simply convention. Such contractions are not informal or colloquialism, but rather follow formal rules.
The contraction of 南無, which is ordinarily read as namu
, and instead pronounced nam
by some, is on account of the following syllable being myo
. This is another contraction that follows formal rules having to do with to consecutive syllables starting with the same sound, in this case, "m".
The fact is, Nichiren never, as far as I know, wrote out the Daimoku in phonetic characters - which he could have. As such, we don't know how he pronounced 南無妙法蓮華経.
Mark, who goes around the internet making a big deal about this and using it as a basis to condemn others, has no textual basis for his criticism. Its just more rancor. He only has his tradition, which it should be pointed out, traces back to a person who does not have a personal lineage back to Nichiren himself, but comes from reading Nichiren's writings divorced from a personal teacher.