This is a complete nonsense: it is mixing an economic model with a taxation, gets to social ideas that are anti-economic (why bother having an economy at all if you do redistribution?) and throw the magic word "equitable" in it, all without any supporting argument. It is amazing, better crafted than demo scene.

What do you think would happen with an aggressive capital gains tax (including on unrealized gains) and negative interest rates?

I'd expect movement of capital away from that economy and a 20+% recession in that economy.

Where would capital move?

Anywhere? Panama, Cayman Islands, bitcoin, foreign real state, gold... take your pick. Wealth is pretty fluid these days, even for people who live under Chinese-style capital "controls".

Tax evasion is not a valid answer. The others are issues though gold would be subject to the same taxation. Moving money abroad is a major issue but its already a major issue (see apple in Ireland or Chinese in Australia).

If that is the only argument, it does not hold.

I'm not sure if you are replying to me or the parent but I'm asking a genuine question. If capital needs to move from investments where would it go?