(I meant 20 + 30, not 20 + 50, sorry for the confusion.)

I don't think I understand in what ways it can be damaging to reputation. Maybe you mean if I pretended to be the original author? Because in that case I think it's a different issue than copyright. You can have no copyright but still have laws about proper disclaimers and proper attribution, and I'd be in favor of that. I don't care if I have to clearly and explicitly label all my derivative works as a "fanwork", so long as I'm allowed to legally make and distribute them at all.

Other than that, you mentioned "multiple kinds of social harm". But I'm looking through your other comments on this submission, and the only other place where I've found where you explicitly state a harm is here:

> That claim doesn’t hold water when the pirate is enjoying the value of the work, and is ignoring the costs of it’s creation including time.

Which as far as I can tell is just the money issue again. Sorry if I missed another harm that you mentioned, but for now as far as I can tell every harm is either money, or a harm which can be addressed by much less restrictive laws than copyright.

Now, assuming that money is the only harm of copying, which is what I believe, then it's the only issue that copyright needs to deal with. And given that copyright has harms of its own, both socially and with respect to freedom*, then once money is dealt with I think the copyright should be removed.

So then it becomes a debate on what would be a "reasonable" copyright, which would mostly avoid the "money" harm, while also mostly avoiding the harms of copyright itself. I don't think it makes sense to reward children for their parents' creation (except insofar as they might inherit money that the parent has already earned), so I think anything longer than life is already much too long.

I think 50 is more than enough, since someone making a work at 20 will be able to receive income from it until they're 70, which is almost their entire life. I think it's very rare that a work will make no money for the first 50 years but then suddenly start making money, but even in that case the author will probably have already moved on, made more works and/or made money in other ways by then, so at that point the monetary harm is less important.

I'm in favor of requiring manually registering to extend copyright past 20 because I think most works will never make money and are not intended to make money (most memes, for example), so those works should become public domain faster. I also think that most works that make money will have started doing so in the first 20 years, so it will be rare that a money-making work will unintentionally enter the public domain after 20 years.

I'll note that I'm less confident about registration than about shorter copyright. However, I view the "manual registration" as a compromise, so if we removed it and just went for a flat number of years, I would advocate for less than 50 years, maybe 30 or 40.

(*I think it's a restriction on my freedom that I have things in my head which I can't use. It wouldn't be realistic to argue that I should avoid looking at any copyrighted material my entire life, and as long as I can't feasibly do that and still take part in society, I will have ideas derived from copyrighted works and be unable to legally act on them)

Edit: I should also address startups and corporations making software. In that case, 50 years is already quite long, and the software almost never stays exactly as it is, it evolves. And every new change will last another 20-50 years. So you'll only be able to use version 20-50 years out of date, so in almost all cases the corporation will still have their competitive edge.