There are two kinds of people:
...those who enjoy dark humor and those who had their legs amputated.
...those who understand this joke and those who understand paradoxes.
This is very good. At first glance, formatting of the post would suggest that the topic sentence has correctly signposted that two descriptors are to come, and indeed two 'bullets' appear. However, depending on the reader's interpretation of the relationship between the coordinating conjunction "and" and the second occurrence of the demonstrative pronoun "those" in each bullet, it is unclear which of the following is being represented:
a) "kind of people" #1 is that population formed by the
intersection of those enjoying dark humor and those having both legs amputated, and by extension "kind of people" #2 is that population formed by the
intersection of those that understand the joke and those who understand paradoxes, OR
b) two kinds of people are listed in the first bullet, and two MORE kinds of people are listed in the second people, for a total (at a minimum) of FOUR kinds of people rather than the two that were signposted.
This perceived lack of clarity is clearly the very basis of the paradox referred to therein, giving rise to a 'nested paradox', if you will - the use of the word paradox within, rather than as a signpost for, the actual paradox.
Semanticists and/or pedants may argue whether this was truly a paradox, and grammarians may argue as to whether the second use of the demonstrative pronoun in each bullet makes it clear that there are two populations described in each bullet. Nonetheless, the overall effect is both subtly funny AND paradoxical, fully qualifying it for the thread. Masterful, indeed.
TL;DR - Venn diagrams are your friend.