न हसन्ति मुनीश्वराः

चक्षुर्भ्यो हसते विद्वान्दन्तोद्घाटेन मध्यमाः।

अधमाः अट्टहासेन न हसन्ति मुनीश्वराः॥

२२२१

cakṣurbhyo hasate vidvāndantodghāṭena madhyamāḥ|

adhamāḥ aṭṭahāsena na hasanti munīśvarāḥ||

2221

A mature and very learned person smiles, laughs etc… that is signifies his emotions through subtle movements of his eyes.. that is he laughs through his eyes

A mediocre person exhibits his emotions just as they arise, by open gestures.. the mediocre man laughs exhibiting his teeth widely

An immature person of lowly tastes exhibits his emotions in a bizarre showy way.. the lowly person roars and roars when he has to laught

And the ascetic, the renunciate, never gives expression to his emotions at all.. the muni or the sage never laughs.

This slokam showcases the various levels of human maturity.. It does not necessarily mean that all fellows who do not smile are sages.. And a fellow who roars with laughter when there is a rare occasion to be very happy in not a lowly fellow. The statement has to be interpreted in the right perspective.