Answer

No, it is not considered wrong in Jain Dharma to chant Om as a sacred syllable, but Om is not part of the original Navkar Mantra.

Explanation

The Navkar Mantra is traditionally recited as:

• Namo Arihantanam
• Namo Siddhanam
• Namo Ayariyanam
• Namo Uvajjhayanam
• Namo Loe Savva Sahunam

In its pure traditional form, “Om” is not included inside the Navkar Mantra.

At the same time, in Jain usage, Om is also respected as a sacred sound that can symbolize the five परमेष्ठी. So:

• Chanting Om separately is not inherently wrong
• Adding Om inside the Navkar Mantra is not the original form
• For the most authentic recitation, many Jains prefer to chant the Navkar Mantra exactly as it is

Spiritual Understanding

In Jain Dharma, the main focus is on:

• devotion with purity
• correct remembrance
• preserving the original sacred form of the mantra

So the safest and most traditional approach is:

• Recite Navkar Mantra in its original form
• If you wish, chant Om separately with reverence
• Do not let the addition change the meaning or original structure of the mantra

Takeaway

Om is respected in Jain tradition, but it is not part of the original Navkar Mantra. For pure and traditional recitation, chant Navkar Mantra as it is.