*Inspired by [this question on meta.cstheory.SE](http://meta.cstheory.stackexchange.com/questions/1381/comment-templates). The post [at meta.Tex.SE](http://meta.tex.stackexchange.com/questions/430/text-building-blocks) is quite impressive.*

We often leave generic comments to OP and answer posters such as: "if this is a homework, please add a tag," and such. Can we make this post a community wiki and add a big list of standard comments? Let's annotate the usage cases, so other users and copy-and-paste whenever applies.

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As usual on meta, (down/up)vote if you (dis/)agree.

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*Update:* To facilitate copy & paste, if your comment contains links and/or formatting, please enclose the whole text between single inverted quotes: \`...\` i.e. verbatim `like this`.