Does the Prophet's receiving Zayd ibn Harithah naked—as mentioned in Sunan al-Tirmidhi—indicate a lack of chastity and manners, and is there any promiscuity in it?

The advice is not to enter forums that attack Islam unless one has sufficient knowledge to defend it. The aforementioned Hadith is weak because its chain of narrators contains weak narrators (Ibrahim bin Yahya al-Madani and Yahya bin Muhammad al-Darir). Even if we assume its authenticity, the explanation of the Hadith found in "Tuhfat al-Ahwadhi" indicates that the Prophet, may Allah bless him and grant him peace, kept covered from his navel to his knee. The meaning of "naked" (ʿuryānan) in this context is merely that his cloak fell from his shoulders due to extreme joy, and not that he was completely naked. This interpretation aligns with his, may Allah bless him and grant him peace, urging to cover one's awrah (private parts) and maintain chastity.