It seems awfully convenient that do be able to ask a clarification or an update, one should have already answered a bunch of unrelated questions.
That is correct and on-purpose. The goal of any Stack Exchange site is to be a body of knowledge in the form of Questions and their Answers. No chit-chat, no distractions.
Assuming one answers 10 or 20 questions first, how does that make them any more worthy of commenting on another, unrelated, question?
This motivation is exactly why the limit exists. A lot of new users from around the internet are used to (and some feel even entitled) that they can leave their trail of breadcrumbs anywhere. Not so on the sites in the SE network. We want to get rid of that noise, those unwarranted and often unneeded hints and tips from the casual passer-by.
It stands to reason that people with too much time on their hand spending too much time here would have less knowledge about technical subjects, not more... You know, because experience.
Exactly. The communities here have gathered hundreds of experts on their subject and they landed and stayed here instead of anywhere else because the sites are heavily moderated, curated, community edited and free of frivolous comments.
I tried dipping a toe in the StackExchange game today and all I see is a bunch of gatekeeping... You might argue that it helps keep the community "healthy" or whatever excuse. But the results speak for themselves, some questions here will stay unanswered, uncommented forever. Wouldn't being more welcoming of new commenters be more productive?
The gate keeping is the key factor to the success of the sites. You're free to dislike that. It is not an excuse, it is a well thought out design principle at the heart of every SE site. We don't think an unanswered or uncommented question is a problem. Those will either be removed/closed if they don't get views and/or votes or they receive an answer later.
This kind of universal approach to reputation only encourages answering easy questions, and penalizes highly technical questions that will not get many answers or many upvotes.
Given we have enough easy questions we probably have the answer already and therefor a duplicate applies. The difficulty or the question doesn't matter. Whether the question is unique, on-topic and has value for future visitors is all that matters.
None of this makes sense for a very old and widely known website, which should have matured into being efficient by now... Unless this limitation is actually there to force newcomers to answers questions as a way of gaining enough reputation to do what they actually intended to do in the first place.
It does make sense because it wasn't all that obvious from the start 6 to 8 years ago that this model would be successful. Specially given the fierce competition from an hyphenated site and of course Yahoo Answers.
The SE network is not the only place on the internet with textboxes where users can type text in and then have it served for many years. Heck, there are even various spin-offs that copy or expand on the Q/A model.
Users here participate because they want to share their knowledge and to do so in a moderated, curated and relatively noise free site. That needs adaption for users that are new to the concept. I give you we might need more side-wheels for those new users to get them past the seemingly useless hurdles. Those hurdles exist for good cause and the community here embraced them and that made their communities successful. It is not a given that removing the entry barrier makes a community better. Other sites can do that as they wish. We stick to what still is successful.