You are are applying the standard definition of rent/rent seeking used by economists. But MichaelBurge's post is using the language of the original article, which claims that renting out an apartment, or making capital gains from a business, "rent seeking".

So MichaelBurge is making a valid critique of the original article, whether or not the article was correct in using the term "rent seeking"

The original article is naively expanding the definition to include simply "owning things which are worth money/time", i.e. the time value of money is somehow rent-seeking corruption.