Abū Saʿīd al-Himyari from Muʿādh, yet Abū Saʿīd never met Muʿādh, so the chain is broken.

As for the weakness of al-Ṭabarānī’s additional wording, it is because Furāt ibn al-Sāʾib appears in the chain, and he has been declared unreliable and abandoned.

Lexical notes on the ḥadīth:
• al-lāʿinayn (dual form): al-Khaṭṭābī said, “It refers to the two actions that bring upon their doer the people’s curse.”
• al-malāʿin (with an open first vowel): plural of malʿan, meaning a place that incurs cursing.
• al-thalāthah (the three): in the accusative case, functioning as an adjective describing al-malāʿin.
• al-nās (people): derived from nāsa yanūsu, “to sway or move about.” Its diminutive is nuways. It is used as a collective noun—like raḥt (band) or qawm (folk)—while its singular is insān, which differs in form. The original pronunciation was al-unās, but the hamzah was dropped through frequent use; hence, when uttered without the definite article, the form anās is more common than nās.
• yatakhallā (to relieve oneself): taken from khallā, “an empty place,” because anyone who wishes to answer the call of nature customarily withdraws from people to a secluded spot. In the ḥadīth it specifically denotes defecating in people’s pathways or in their shade; it is a polite euphemism for an unseemly act.
• al-mawārid (watering places): plural of maurid, the spot to which people come for water—be it a spring, a pond, or the like.
• al-barāz: an open expanse of ground, used here as a euphemism for human excrement. Literally it is a low-lying piece of land, and the filth of man was named after it because, in relieving himself, a person seeks such a depressed spot.
• al-ṭarīq (road): morphological pattern faʿīl with the sense of mafʿūl, i.e., “trampled,” because people’s feet continually tread it. Its plural is ṭuruq (with two ḍammahs). In the dialect of the people of Najd it is masculine, and that is how it appears in the Revelation, as the Almighty said: