Here’s a list of common comments for Math.SE newbies.
I’ve posted them on WordPress.com, but I often got typos after updating that page.Without version control, it’s hard to find out the cause of such error.
Questions lacking context
[Welcome to Math.SE!](//math.meta.stackexchange.com/a/11168/290189) Please read [this post](//math.meta.stackexchange.com/a/9960/290189) and the others there for information on writing a good question for this site. In particular, people will be more willing to help if you  your question to include some motivation, and an explanation of your own attempts.
Questions not written in MathJax
[Welcome to Math.SE!](//math.meta.stackexchange.com/a/4928/290189) Please use MathJax. For some basic information about writing math at this site see e.g. [basic help on mathjax notation](/help/notation), [mathjax tutorial and quick reference](//math.meta.stackexchange.com/q/5020/290189), [main meta site math tutorial](//meta.stackexchange.com/a/70559/290189) and [equation editing how-to](//math.meta.stackexchange.com/q/1773/290189).
To avoid excedding the upper limit of 500 characters, I’ve copied and pasted several comments and combined them into one.
[Welcome to Math.SE!](//math.meta.stackexchange.com/a/4928/290189) Please use MathJax. See [mathjax tutorial and quick reference](//math.meta.stackexchange.com/q/5020/290189). Please [don't use pictures for critical portions](//math.meta.stackexchange.com/a/20529/290189) of your post. Pictures may not be legible, cannot be searched and are not viewable to those who use screen readers. Please read [this post](//math.meta.stackexchange.com/a/9960/290189) for information on writing a good question. People will be more willing to help if you  your question to include an explanation of your own attempts.
Please do [not use pictures for critical portions](//math.meta.stackexchange.com/a/20529/290189) of your post. Pictures may not be legible, cannot be searched and are not view-able to some, such as those who use screen readers.
Displaystyle in question title
I have changed the formatting of the title so as to [make it take up less vertical space](//math.meta.stackexchange.com/a/9686/290189) -- this is a policy to ensure that the scarce space on the main page is distributed evenly over the questions. See [here](//math.meta.stackexchange.com/a/9730/290189) for more information. Please take this into consideration for future questions. Thanks in advance.
One question per post
Please, post only [one question in one post](//math.meta.stackexchange.com/a/7132/290189). Posting several questions in the same post is discouraged and such questions may be put on hold, see [meta](//math.meta.stackexchange.com/q/6464/290189).
Fractions in indices and exponents
Please [don't use `\frac` in exponents or limits of integrals](//math.meta.stackexchange.com/a/5057/290189).
Notify question writer for a $\LaTeX$ edit
[Welcome to Math.SE!](//math.meta.stackexchange.com/a/8588/290189) I have tried to improve the readability of your question by introducing [$\rm \LaTeX$](//math.meta.stackexchange.com/q/5020/290189). It is possible that I unintentionally changed the meaning of your question. Please proofread the question to ensure this has not happened.
Some commonly misused tags.
[Probability theory](//en.wikipedia.org/wiki/Probability_theory) is [about the measure-theoretic foundations](//math.meta.stackexchange.com/a/8587/290189) of stochastics. The tag ([tag:probability-theory]) should be used for questions concerning this subject, not for questions about calculating a specific probability. Use ([tag:probability]) instead, see also [meta](//math.meta.stackexchange.com/q/1686/290189).
The tag ([tag:functional-analysis]) is [intended for questions about infinite dimensional vector spaces](//math.meta.stackexchange.com/a/8587/290189), there is a separate tag for ([tag:functional-equations]); see the [tag-wiki](https://math.stackexchange.com/tags/functional-analysis/info) and the tag-excerpt. (The tag-excerpt is also shown when you are adding a tag to a question.)
The tag ([tag:algebraic-geometry]) is [intended for questions in a branch of mathematics called algebraic geometry](//math.meta.stackexchange.com/a/8587/290189) (see the [tag-wiki](https://math.stackexchange.com/tags/algebraic-geometry/info).) The tags ([tag:algebra-precalculus]) and/or ([tag:geometry]) should be used for basic problems that involve both algebra and geometry.