Reviewed the definitions on Merriam-Webster, mostly confirms my usual usage:
2: of a specific but unspecified character, quantity, or degree: the house has a certain charm
Means you want to qualify something or somethings based on a characteristic, but it's vague or unknown to you.
1: of, relating to, or being a single person or thing: the particular person I had in mind
3a: distinctive among other examples or cases of the same general category : notably unusual: suffered from measles of particular severity, This computer program will be of particular interest to teachers.
b: being one unit or element among others: particular incidents in a story
So 3b is the generic interchangeable definition, but the distinct definition of particular is when you want to single something out, or highlight it for being notable.
1a: constituting or falling into a specifiable category
b: sharing or being those properties of something that allow it to be referred to a particular category
2a: restricted to a particular individual, situation, relation, or effect: a disease specific to horses
b: exerting a distinctive influence (as on a body part or a disease): specific antibodies
3: free from ambiguity : ACCURATE: a specific statement of faith
When you are grouping something into a defined category, or when something is made for a purpose or effect unique to itself, then it's specific.
Hopefully this helps clarify some things. And my opinion on language is that it's all based on how people use it, so there's no wrong answer so long as the speaker or writer's intended meaning gets through.