If you get good value out of Signal and you can afford 5, 10 or 20 bucks a month get that auto-donate signed up. I can't think of a more cost effective way to directly contribute to practical privacy.
Will Apple still able to get the 30% cut if I do using in app payment? Any idea? Does it make more sense to sign up for monthly donation via web to get more money donated to Signal vs not getting a badge?
Is it different? I just did it via app without a second thought.
If you only get the badge via app I think it's better even if a chunk is taken by the app store, because then people ask "wtf is that heart thing?" and then I can tell certain contacts what it is get them to do it too.
If you are using In-App Purchase then yes, for almost whatever it is (I think they might have at least a couple special deals with major publishing companies... not Signal ;P) you are "donating" 30% of your money to Apple.