You are entitled to your opinion but as someone that has built an authority site I know the directory submissions "help". They are not a concrete sure fire way to brand or build authority, but it is 1% of the puzzle.
As for commenting on edu sites, Google's own blogs says that they discount these links because they know what marketers have been doing.
Originally Posted by Econtinue
Directories will create a backlink to your site, but will have little to no effect on ranking. Even if your website is in a specific category, there's nothing relevant that would add any value to your link.
Find few edu blogs to comment on. It'll have a lot more effect on your ranking...
And in my opinion this has nothing to do with branding. Branding comes from content, credibility and authority status (not authority website). Spreading links doesn't mean you're branding yourself or your business. In a website directory your link isn't really exposed to targeted prospects, so branding can't really be the purpose of submitting your site to it.