Marking something as 'low content' is not just to make people tack on nonsense to the end of 'lol' in order to make it appear constructive to the discussion; the theory is that you will actually contribute, not change 'lol' to 'lol I was laughing etc. etc.' or 'I quite enjoyed a hearty chuckle from the hilarity of this situation,' but to change 'lol' to something more meaningful--to something which ACTUALLY adds value to the discussion.
An unfortunate side effect of this low-content-pruning is verbatim reiteration, in many cases; just in reading these first two pages of this thread, you can see that many people wrote a few sentences, all of which state (but do not explicate) 'the low content limit is there so you don't just write one-word responses.' I feel that this can be attributed to the declining attention spans of internet users, as discussed in 'Is Google Making Us Stupid' by Nicholas Carr [http://www.theatlantic.com/magazine/archive/2008/07/is-google-making-us-stupid/6868/], wherein the author describes how the Internet has had the unfortunate malediction to weaken attention spans. Judging by the deluge of similar responses to this thread, I would suggest that many of those replying did not read what others had to say, and simply contributed their own thoughts. While I believe everyone has a right to his opinion, a discussion gets nowhere if people constantly retread old ground. In a discussion, everything submitted should be relevant and grow upon what exists.
Further, to discuss the 'A picture is worth a thousand words' argument, I submit to you the above example, albeit using a link in lieu of a picture or video. When implemented properly as part of an argument, a picture, video, article, etc. can bolster the argument. When a meme or otherwise simple picture has nothing constructive to add to the argument, it wastes space, proliferating the waning attention span, because people are drawn to the picture before the text, and if everyone just posts pictures, why bother reading the text at all (especially if it contributes nothing to the argument)?