It would seem quite an essential liberty for a democratic polity to be able to impose this thing called "taxes". I suppose it's up to you to decide whether that is compatible with the rule of law and property rights.
We already have taxes, the vast majority of which are paid by the wealthy. Taxes are not a cap on allowable net worth. That is a different thing altogether. That is economic suicide.
Most of the rah rah billionaires shouldn't be allowed people are just proposing a wealth tax from what I've been told. If I'm wrong I'm open to hearing about it.
Wealth taxes are also economic suicide but most of the "rah rah billionaires shouldn't be allowed" people seem to have absolutely no idea how anything works and think billionaires have billions of dollars sitting in their checking accounts and they could easily write an "end homelessness" check but just don't because they're mean.
I don't really care to advocate much for wealth taxes since I don't particularly like them over other options. I just don't think imposing wealth taxes (even if they're progressive to the point that it's higher than the average growth rate of, e.g., equities, or maybe even just the risk-free rate when wealth is in the billions) is something that ought to be considered "how dictatorships work".
So you know, agree to disagree, I'm not going to argue anything other than that I don't particularly care for the framing of it as dictatorial or mob rule because the same can be done for other taxes. Which I have done and it doesn't appear you wish to dispute anyway.
Once again, OP is proposing not a tax but a wealth cap. A tax takes a percentage of whatever - income, wealth, transaction. It does not impose a limit on how much you are allowed to have. That is an entirely different phenomenon. We do have a whole constitutional amendment about the government unreasonably seizing your property and saying "well if it's more than this amount the government gets to take it all" is an unreasonable seizure of property.
I assume by OP you mean chipotle_coyote, which, reading their comment again, does not propose any specific policies and in fact explicitly disclaims knowing the specific best policy for the policy outcomes that they desire, which is anything that adresses the level of wealth inequality we currently have.