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I have noticed some people putting something like $\$\{\}\{\}\{\}\$$ at the end of their comments (for example, André Nicolas' comment here). I can see the curly braces fast enough because MathJax doesn't load fast for me. Why are there curly braces at the end of the comment? What do they do?

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    $\begingroup$ They make the submitted text long enough for the character minimum ($15$ characters) $\hphantom{\text{some place holder text for length ;)}}$. $\endgroup$ – Daniel Fischer Mar 21 '14 at 18:33
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    $\begingroup$ I do not know whether it was discussed on this meta, too, but on MO some people complained about it. $\endgroup$ – Martin Sleziak Mar 21 '14 at 18:36
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    $\begingroup$ you can also use $\tiny\phantom{phantoms...huh...}\! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! \! $ $\endgroup$ – draks ... Mar 21 '14 at 21:42
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$\begingroup$

As remarked above in the comments (and in a now deleted answer), some users use ${}{}{}{}{}{}{}$ to overcome minimum length requirements in comments (and answers, too). This is rendered as... pretty much n${}$oth${}$ing, though Math${}{}{}{}{}$Jax does have to render its nothingness.

Zero-width spaces (and related characters) can also fill this purpose, but they are not as commonly known in the math community (and are somewhat more difficult to input). there​are​zero​​width​spaces​here​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​width​spaces​here​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​.

In answers HTML comments can also play this role: <!-- html comments -->.

Since the SE markdown is largely ignored in comments, HTML comments and HTML character codes in comments are displayed verbatim. However, you can manually input special Unicode characters. The zero-width space is U+200B. For example, on Windows you can input this by pressing and holding the Alt key, pressing the + key on the keypad then the hexadecimal Unicode value, and then releasing the Alt key: Alt +200B yields: »​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​« not much to see, unfortunately.

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  • $\begingroup$ Too short:​​​​​ $\endgroup$ – user642796 Mar 21 '14 at 20:45
  • $\begingroup$ Nearly too long: ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ $\endgroup$ – user642796 Mar 21 '14 at 20:46
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    $\begingroup$ &#8203;&#8203;&#8203;&#8203;&#8203;&#8203;&#8203; $\endgroup$ – user642796 Mar 21 '14 at 20:47
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    $\begingroup$ ​​​​​​​​​​​​​​​​​​​​​​​​​ $\endgroup$ – Michael Greinecker Mar 21 '14 at 21:18
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    $\begingroup$ So why do we need a minimum length when the workaround is trivial? I use it too, I confess... $\endgroup$ – draks ... Mar 21 '14 at 21:42
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    $\begingroup$ @draks...: I would guess that the main reason for minimum comment lengths is to reduce the number of "thanks"-only comments (which most other SE sites are not as accepting of). I wouldn't call these workarounds trivial, as they require some knowledge of the system or the way computers work, and often it's easier to just include one or two extra words. $\endgroup$ – user642796 Mar 21 '14 at 21:59
  • $\begingroup$ ok ${ }$ ${ }$ ${ }$ $\endgroup$ – draks ... Mar 21 '14 at 22:08
  • $\begingroup$ Too short$\qquad$\qquad. $\endgroup$ – Américo Tavares Mar 22 '14 at 0:06
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    $\begingroup$ @draks Even if Dollar signs and such were not counted in the character limit, one could just put "15char 15char 15char" at the end of their post, which accomplishes the same thing in a less subtle way. $\endgroup$ – MCT Mar 22 '14 at 18:14
  • $\begingroup$ Thank you very much for your answer. (Is really the neatest way of saying "thanks" and doesn't require special characters...) $\endgroup$ – user1729 Mar 23 '14 at 15:46

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