I've seen several answers that begin with "tl;dr" or "TLDR". I had to look up what this means. The Urban Dictionary says "too long; didn't read".
Examples (but not the worst ones, which I can't find again):
This seems like incredibly bad form to me. Aside from being cryptic geek-speak, I cannot tell who wrote it, or what it is supposed to communicate. I can imagine two possibilities:
1) The questioner wrote it to inform the answerer that their answer rambled. If so, it is disrespectful, obtuse, and this should be a comment under the answer.
2) The answerer wrote it to indicate that they are providing a synopsis of what they wrote. If this is the case, they should be writing in plain english.
My instinct is to delete this with prejudice. Is there any reason we should tolerate this at Skeptics?
addendum: This notation is clearly accepted among this community as a jokish Netizen idiom, so it is what it is. Having read the responses, I have these parting thoughts on the topic.
1) Many scientists make a conscious effort to avoid jargon when speaking with non-experts, (and even experts) based on the belief that it interferes with communication. They believe that gratuitous use of jargon ("fancy words") creates the impression of pretentiousness and exclusivity. Some have even attempted to quantify the amount of jargon, or created communication games such as Up Goer Five, to help train scientists in avoiding jargon (FWIW, I gave up when I discovered that "plant" was not an allowed word). Even aside from scientific jargon, many other writers have developed tools to help them make their writing more accessible. These issues were also discussed by George Orwell in his essay "politics and the English Language" (tl;dr) this stuff matters.
2) The notation "tl;dr" has been added to the Oxford Online Dictionary. I still think it's a fad existing within a narrow subculture, and it looks like some sort of misformatted markup rather than an abbreviation of a phrase. More than once, I've failed to communicate when I've used abbreviations like FWIW or BTW, even though those are the initials of words in common phrases. In contrast, the definition of tl;dr is extremely derived, and of recent origin.
3) Use of TL;DR at the beginning of a comment is probably not needed most of the time. That is also where I found it to be the most distracting/confusing. Many commonly taught writing styles emphasize that the first paragraph should contain a succinct statement of the thesis, so there is no need to warn readers that you are doing so. For instance: The Five Paragraph Essay, and the Inverted Pyramid (journalism)
p.s. I feel like this rant should go on my personal profile page, but that doesn't seem to be how things are done here.