How many

Whew! Not so easy, Jobb, because your structure does not reveal your precise meaning. Try this:

'In the discussions on this forum, how many have we seen who, possessing the abilities of independent thinking and analysis, emphasize substantiation and logic?'

I meant
" How many have we seen emphasize substantiation and logic, and how many have we seen possess the ability of independent thinking and analysis?"

Ah.

Well, you can use my previous sentence subordinating the 'possession' clause; or if you wish to coordinate, you had better use:

'How many have we seen emphasize substantiation and logic, and how many have we seen who possess the abilities of independent thinking and analysis?'

We can observe the act of emphasis, but we cannot observe the act of possession,

Thanks for inspiring!

Jobb, this sentence is far too long. How about this:

Among the forum's participants, how many emphasize substantiation and logic? How many are capable of independent thinking and analysis?

That is cool!