"You can just type LaTeX formulas between dollar signs!"

And that's what should be changed to avoid the "But I can do it in LaTeX" attitude. The problem is that most probably do not distinguish between "like" and "identical[ly] to". It's those peculiarities that catch people out and if there's a big notice saying "This site uses MathJaX to display equations" with a link to a help text of what you can and can't do, it would make it easier for people to realise that MathJaX is not LaTeX but very similar.

In other words, we do expect Mathjax to behave like Latex. (That's "like", not "identically to".) Indeed, we're encouraged to do so: when you ask a question, the first sentence of the prominently-displayed help is "You can just type LaTeX formulas between dollar signs!" And I think most of us here operate successfully on the principle that MO-Latex is a scaled-down version of normal Latex, with some added peculiarities. Whether or not that's breaking the bounds of reason, I think that's how most of us do it, and it usually works.

1. One of the great things about a Q&A site is that when someone doesn't understand an answer, they can ask a fresh question and get further explanation. So when someone read the question that Mark linked to and felt that they needed further clarification, instead of dismissing the entire site with a pointless comment, they asked a fresh question: http://tex.stackexchange.com/q/21173/86 and got a more detailed answer.

2. MathJaX is not (La)TeX and expecting it to behave like it is breaking the bounds of reason. TeX can do so much more than MathJaX. The best thing people can do to stop others getting confused is to stop referring to it as LaTeX. We get questions about MathJaX on TeX-SX and they are closed as "off topic" because the underlying engines are so different that expertise in TeX does not help one at all in helping solve the typical problems one encounters in MathJaX.

3. @Geoff: Don't spoil our fun. If you didn't leave us these little puzzles to solve then we'd end up being more disruptive out of boredom so it's in your own interest not to belittle our efforts.

It's not exactly a "hack" (to quote François's opening message), but it's one of the ways in which MO Latex differs from ordinary Latex, and it's therefore something we might usefully keep in mind when negotiating the transition to 2.0.

Make sure you actually mean to start a new paragraph wherever you have a blank line.

My point exactly.

Another advantage of \[...\] over $$...$$ is that the first has distinct begin/end symbols while the second is ambiguous.

Why is this an advantage? Brackets are perfectly legitimate mathematical symbols, whereas dollar signs are not. With the \[\] notation I find myself constantly confused, because I have to decide whether the brackets belong to the formula or are simply delimiters. The fact that \{\} typesets ordinary braces (very much unlike \[\]) is not very helpful either.

Posts that use \cr as a replacement for \\ will be unharmed. This issue may also affect other types of tables: definition by cases, split equations, etc.

The difference can be appreciated by typesetting the following in a plain article (without loading any packages).

This part of the document is to test a
\[very\ long\ displayed\ equation\ surrounded\ by\ square\ brackets\]
without breaking the paragraph.

This part of the document is to test a

\[very\ long\ displayed\ equation\ surrounded\ by\ square\ brackets\]
breaking the paragraph above but not below.

This part of the document is to test a
$$very\ long\ displayed\ equation\ surrounded\ by\ double\ dollar\ signs$$
without breaking the paragraph.

This part of the document is to test a

$$very\ long\ displayed\ equation\ surrounded\ by\ double\ dollar\ signs$$
breaking the paragraph above but not below.

I think the outcome is an important lesson in LaTeX: Make sure you actually mean to start a new paragraph wherever you have a blank line.

Another advantage of \[...\] over $$...$$ is that the first has distinct begin/end symbols while the second is ambiguous.

I'd been using LaTeX for about ten years before I ever heard of the double dollar.

If you learned LaTeX the way I think most of us did (reverse-engineering other people's .tex files), then you must have had better examples than I did. I'd been using LaTeX for about ten years before I ever heard of \[...\].

In case that wasn't clear, the way that the sandbox interprets \\{ is the correct one. The way this works on MO now is that markdown interprets \\ and feeds \{ to mathjax. (In particular, \{ does work when backticks are used.)

I've never used $$ for displays except on MO and the n-Category Café: all the actual LaTeX I write uses \[ ... \]. Indeed, I thought that was the approved LaTeX way of doing things: I don't think Lamport's book even mentions the possibility of using $$. (Is it some leftover from plain TeX?) I'd been using LaTeX for about ten years before I ever heard of the double dollar.

Although I'm now used to having to do this differently for MO, and rarely forget, it tripped me up at first, and I imagine it will continue to trip up newcomers until it's fixed.

Edit: Ah, tricky. Using an invisible unicode character with 0 width. I got it to work with U+FEFF, but my hex editor says that you did it with U+200B

I believe that for $ environment \\{ might work, but in $$ the double \\ is translated to a new line, and then the { breaks off completely.

To get a newline, add the TeX $$ $$
To get around the character minimum, add the TeX $ \hskip 0 em $ (verbatim). This is exactly 15 characters and allows the posting of empty comments.

• You can use the sandbox to test things out on MO 2.0.

• You can also use our fakesite to test things out on MO 1.0 without disrupting the main site.

In another thread, Emil J pointed out that the "backticks hack" that is frequently used on MO 1.0 will not work on MO 2.0. This problem has already been corrected in the sandbox.