@echo vowel

In PC Sanskrit, the /H is a voiceless hiss sound that only happens —

(A) after a vowel and before a pause (by kharavasAn...), and

(B) after a vowel and before k क् kh ख् p प् ph फ् (by kupvoKkaFpauca).

Yet, you will hear lots of speakers that add after the hiss a repeat of the previous vowel. So instead of

namonamaH.
zAntiH.
guruH.

they will say

namonamaHA.
zAntiHI.
guruHU.

This repeat is called an echo vowel.

Because of a centuries-long tradition, adding an echo vowel is compulsory when chanting verses or sUtras, but only if the H ः is at the end of the verse or sUtra.

It is also compulsory af half verse, but only when you make a pause at half verse.

In any other circumstances, adding an echo vowel after H ः is arguably an /apANinIya. But it is done so often, (and wrongly taught so often), that many people (particularly in the Hindi-speaking area) believe that it is compulsory.

So even if /pANini does not mention echo vowels at all, you should consider that they are always optional.

And please don't despair when you meet people that add it wherever they can and where they cannot, and instead of

bhavato nAma kim भवतो नाम किम्

ask like

bhavataHA namaHA kim?

An old saying goes, na buddhi-bhedaJ janayed a-jJAnAm न बुद्धिॱभेदं जनयेदॱज्ञानाम्, don't waste your time making the ignorants more confused.