It's not just a tax: i'm pretty sure the main reason it went up is to see if it helps with Sybil problems.

At 10% it still makes sats to zap your own content to get it more attention. If a stacker zaps their own content with a 10k sat zap from another account they control, the zap only costs them 1k sats (at the old 10% rate). If the stacker can garner at least 1k sats from other stackers, they're net positive and are probably on SN front page for a while, regardless of the quality of the content. At 30% maybe the calculus changes a little.

It's talked about in the release here: #692150

I do miss your writing, though. Would love to see something new!