> It's quite inconsistent though which is really frustrating. I can look at the imgur homepage feed, but if I go into a specific post and accidentally click anywhere it throws a modal up that can't be dismissed.

That's not inconsistent, that's a deliberate dark pattern that every social media site uses. Let them see the first page, then when they want to engage: force creating an account.

When you just put a "log in to see this page" up front, people will bounce. When you have them engaged a little bit, chances are they are already invested enough to create an account.