I think this is great feedback for Known and the indieweb community in general, given with a lot of consideration and kindness. The most important thing is you feel like your site represents you and is fun for you to use and tinker with!
I’m a bit sensitive to the “my site is my business card” aspect too; right now people see a totally random stream of replies that isn’t really me or even necessarily what I’m thinking about today. This may be a good reason to have a super curated front-page feed like @snarfed does, or only show articles like @benwerd does, or only post things that matter like @tantek does.
Absolutely 100% agree that Known’s import/export process is not where it needs to be.
I had an IFTTT recipe for Twitter a long time ago that would copy my tweets into an Evernote document. Something like that is a nice, low-fi way to keep a private archive of them.