@ktmbabu, that is just not true.
-firstly, let me elaborate my comment. this diagram doesnt represent the caste dynamics of nepal in any time period. the caste hierarchy norms were mainly standardised in jayasthiti malla and jung bahadur'S period and this diagram of yours doesnt mach with both of them.this is basically made by some westerners retrofitting nepali castes in indian chaturvarna system.
-khas is indigeneous nepali and traditionally non- hindu .the person who has made this pyramid doesnt know this basic fact.
-not all janajatis are non-caste. they may not have the rules as strict as terai hindus but they do have castes. the char(4) jate gurungs are above the sorha(16) jaate.and the ghale are above them all.rana magar and thapa magar are considered above other magar castes.some magars dont even consider bhujel magars and some do. the thakalis also have a caste hierarchy.. in kirati lands, the traditional jamindars and feudal castes like rai ,subba,dewan still dont intermarry with other kiratis and are called mukhiya ba, jimwal ba,subba etc in villages.the lamas consider themselves superior to other tamang castes.

u talk about there being no fixed restrictions, but there was till the last generation. only the relative poverty and modern ideas have changed that. there are also some newar,magars khas, brahmin,madhesi intermarrying .but economically well off janajatis like gurungs,magars, kiratis and newars still follow their caste hierarchy while marrying.
-just because you (pahade bahun chetri) shuns to talk about caste doesnt mean the idea of social equity and justice wont stop. the thing that everyone misunderstands is that the problem is actually class based and not caste based.when there wa a central feudal lord of khas/thakuri family,there were also local lords of all other ethnic groups who basically were working with the central feudals to loot the common people of all castes and creeds.this is the country where all the 'raiti' of east would go to the subba or rai jimwal of their village ot recieve tika. and the same with the magar/gurung/khas mukhiya of western nepal.the terai brahmins of india would be invited to nepal and granted land and jamindar status by the central feudal king and the jamindars on their side enslaved all others including their owns.
so it was always a class issue.
the caste based identity that is spoken of now was not there till the early 90s as it is now.now everyone identifies themselves with their caste and it has become their primary identity.
the most recent of the caste pyramid that legalised caste system was that of jung bahadur ald it had 3 tiers-
tagadhari( bahun,khas ,newar and terai high castes,including some magars who wore holy thread)
matwali (magar,gurung,rai ,limbu,tamang,newar middle castes)
pani nachalne(all pahad,terai and valley low castes)