So if I save my money, then use that money to buy property and build a profitable farm or a workshop or something else, isn’t that “using wealth to gain more wealth?” This guys’ moral premise is just retarded.

The problem with usury is it is a shortcut to the acquisition of wealth that seems useful, but ultimately leads to far more negative effects down the road. It is based on exponential growth, which is inherently unsustainable whether it’s nature or economics. The excess money needed to feed the system of usury necessarily helps drive inflation. It does this in two ways, one being it puts pressure on increasing the money supply to allow the servicing of ever higher and higher debt. The second being how it bids up the price of goods and property by artificially increasing demand for things. Just look at how the low interest rates drove up the cost of housing and automobiles. The same is true with student loans, with universities being able to keep jacking up the price of tuition, knowing that students would just borrow more money.

Without usury you would not have nearly the amount of asset and commodity inflation you are seeing right now. It hurts everyone, even people who do their best to avoid taking on debt, because inflation affects us all. 

 >So if I save my money, then use that money to buy property and build a profitable farm or a workshop or something else, isn’t that “using wealth to gain more wealth?” This guys’ moral premise is just retarded.

Your money has produced something other than money in that instance. His moral premise is correct. The objection isn't to leveraging wealth, it's to leveraging money 

 This guy isn’t making a neat distinction between money and wealth like you are. Usury involves the lending of money at interest, and money isn’t exactly wealth. Land and capital is not money, but it is wealth. But we often measure wealth in terms of monetary value and this is what the guy is doing here.

People do things like invest money in projects or businesses in order to acquire more money and wealth. If they have land and use it wisely  they can generate a nice revenue stream and improve the monetary value of that land.

This guy just flatly stated that using wealth to make more wealth is wrong. He doesn’t distinguish in any way regarding how this is done, just makes a blanket condemnation. 

 It's a 4chan post that drives at the gist of the issue, it can only go so far. Given the obvious context of the post, I think it's rather pedantic to quibble on how the anon uses the term "wealth."