I take quercitin for allergies and as biased as this will sound, I don't think those studies indicate that it is a risky supplement at all.
As they very nicely pointed out, the studies were done on specific cancer cell lines and genetic lines of rats. What that means in the real world? I dunno but I too think that the benefits outweigh the risks.
The "risks" we are talking about appear to be a potential for reduction(which IMO might lower if it's not needed due to additional antioxidants being present) and a potential for estradiol production but at what supraphysiological doses for humans we don't know. The numerous studies indicating positive benefits far outnumber the negative studies thus far IMHO.
I'll take it until I see more concrete evidence.