That really depends. On the internet nobody needs to know that you are 40 or 50. Finding a permanent job at a SV company may be harder, but freelancing / contracting is not.
I would argue that a company that rejects a competent 50-year-old on "cultural fit" is not worth considering unless you're desperate. That's douchey even by VC-funded startup standards.
That comment says nothing about what percentage of companies are like that. I don't have enough data to know if they're common or rare.
I'd guess that the signal:noise ratio of jobs available at age 50 gets better. Ninety percent of software jobs are shitty, but I also think that companies offering shitty jobs are more likely to age-discriminate, because older people are not likely to fall into the premature emotional investment trap.
