"discussed about which" is a grammatically correct and usable phrase in formal written English.
For example, you could say: "We discussed about which topics to include in the workshop."
Thiel and Slaughter mainly discussed globalization, about which both were pessimistic: Thiel suggested that globalization had led to "nihilistic imitation," in which countries copied one another instead of pursuing innovation; Slaughter worried that globalization, having promised a prosperity it couldn't deliver, was instead breeding "deep anger and resentment".
None of the above authors have discussed about the problems which we are considering here.
It was the first time the father and son had sat down together to discuss "About Alex," which opened this month to mixed reviews, and they were trying to figure out how to relate to each other as fellow filmmakers.
This was arguably implicit in the proposals discussed above, which took claims about ability to be reducible to claims about subjunctive conditionals.
The author makes very clear what this paper is about, which corpora are discussed and where the border is drawn to resources not discussed here.
"Groups of students can be found in colleges discussing topics about which they don't have sufficient knowledge to form opinions and so their learning remains shallow.
Mr. Fuerth can sound downright eloquent when discussing issues about which both he and the vice president feel passionately, like the AIDS epidemic in sub-Sahara Africa.
Although much has been discussed about risk transfer in Sibs, which lie with investors rather than the commissioner, this has never been strictly true.
As I have discussed elsewhere and about which I will continue to harangue everyone for the rest of my professional life, magnificent and largely unprecedented things are about to happen as the implications of our budding age begin to sink in among the citizenry at large, and particularly those of intelligence, honesty, erudition, and good will.
