Replicating the features that require being logged in such as upvoting and commenting is actually not trivial.
I recently built a Hacker News client [0] on top of the official API and using the method described in the article to login users is very inconsistent. I kept running into Captcha issues and even when that didn’t happen, sometimes a login request would simply not return the expected token.
Unless the official API starts offering user login, this will remain difficult.