Merriam-Webster's 'who/whom' dilemma

Please note I don’t need theory on who/whom usage. I need to understand the dictionary’s explanation.

I found the following article on merriam-webster.com recently:

https://www.merriam-webster.com/dictionary/whom

It says:

though now often considered stilted
especially as an interrogative and especially in oral use
—occasionally used as predicate nominative with a copulative verb or
as subject of a verb especially in the vicinity of a preposition or a
verb of which it might mistakenly be considered the object

Is the given explanation correct? I know you can only use whom as an object! But they say it’s occasionally used in a way we might mistakenly consider it as the object. They also provide us with the following example sentence:

people … whom you never thought would sympathize — Shea Murphy

It means ‘I never thought I would sympathize with these people.’ Is that right?

But if we would say: ‘people … who you never thought would sympathize,’
it would mean ‘I never thought these people would sympathize with anyone.’ Am I correct?

Then, based on the explanation, if whom is used as the subject, then in fact we have to use who instead of whom. But occasionally it happens that people use whom when we have to use who. How do I know the exact meaning of this sentence then (based on Merriam-Webster’s explanation)? Should I contact Shea Murphy to provide me with a clarification or what?