What are the rules and regulations pertaining to the principle that a detailed disparagement [Jarḥ Mufassal] takes precedence over a general praise [Ta’dīl], and is it the case that when a detailed disparagement conflicts with a general praise, the general praise take precedence over the detailed disparagement?

Shaykh Muḥammad Bāzmūl:

The scholars have stipulated that disparagement is given precedence over praise, and they have said that when a persons integrity has been established – meaning that the scholars have determined his integrity and trustworthiness – then nothing can be accepted about him other than a detailed disparagement [Jarḥ Mufassal]. And likewise their statements and reports concerning a person whose integrity has not been established and the scholars have not determined his trustworthiness, then a general disparagement (not detailed) is acceptable about him. As for someone whose integrity has been established then nothing is accepted about him except a detailed disparagement [Jarḥ Mufassal]

Then they said that when a detailed disparagement conflicts with a detailed praise – such as what you have mentioned in the question – they say that the disparagement is not rejected except if the one making the praise mentions the reason why the disparagement was made and then refutes it. So for example the one disparaging mentions about someone in relation to his belief [ʿaqīdah], so the one praising says, ‘Yes, he used to be upon this belief but he left it and did not return it.’ or the one disparaging says, ‘He did not memorise the book, but in fact he used to report it from memory.’ So the one praising replied, ‘Yes, he used to be as such but then he returned back and heard from the Shaykh and preserved his source and began to report only from his source.’

Therefore, if the one praising mentions the reasons for disparagement and responds to it, it is accepted with the condition that the one being spoken about is not known to play games and to be a person who follows his desires and a person of deception. Since it has become the case that some people have been praised in detail, whilst at the same time has been disparaged in detail, and this individual is known to play games and to be a person who follows his desires and a person of deception. He is known to be from those who do not submit to the truth nor return to the truth. So in regards to this person, even if the praise was detailed, we do not accept it due to what we know of his condition. And Allah ﷻ knows best.