The first line of the piece attempts to demonstrate the particular stylistic foible being parodied in the form of one short, pithy example. In the case of more plot- or structure-focused critiques, this is not always possible. However, by this, the third sentence, the conceit should have become obvious.
The paragraph break allows me to take a breath after the first joke and perhaps settle into a slightly longer bit which demonstrates the conceit more fully and pushes it a little further than was possible in the first paragraph. Now that the reader is familiar with what’s going on, they will either enjoy this second stab at it more than the first or, having already got the point, they will have completely lost interest.
Reactions to the piece are likely to be mixed, with some comments praising the writing, some contributing their own jokes based on the same formula as the original and, in rare cases, some apparently missing the fact that the work being presented is parody and defending it against other commenters’ derision. Mixed in with these will be comments from people who have noticed typos or errors of usage in the piece – these bits of well-meaning and useful feedback unfortunately tend to come across as being slightly passive-aggressive.
The longer the piece, the more likely it is that I will have outstayed my welcome and worn out the joke by the end, which will tend to fizzle out.