As pravins has notified that Unicode says:
" 0D64 " and 0D65 " are reserved and For viram punctuation, use the generic Indic 0964 and 0965. http://www.unicode.org/charts/PDF/U0D00.pdf . So ideally we should put Malayalam script full stop there."
& Shriramana Sharma has described :
"Dandas may not be required for Malayalam language orthography but they
are required for Sanskrit language orthography in Malayalam script.
Hence all Indic fonts (including Tamil) should contain the danda
characters."
There is need for devanagari danda & double danda in Lohit Malayalam
Problem description : Not aware of the reason behind keeping devanagari danda & double danda in Lohit Malayalam.