Leave the positive stuff on the campaign page, but by all means PM the author if you catch something. Mine had a few tweaks that I fixed that way. In a way, crowd-sourcing puts many more eyes on your novel and work than you alone will ever catch.
But, largely, just pm the author. Not only is that good practice, it helps you form an actual relationship. If a book manages to fund, it will go through extensive editing by people actually being paid to do that. Look at the one or two sample chapters tossed up as sort of a ’beta’ draft of a book for an idea.
If you find yourself judging commas... you are barking up the wrong tree as 99.9% of the drafts on inkshares haven’t been through copy editing yet.