Inspired by this question on meta.cstheory.SE. The post at meta.Tex.SE 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.
As usual on meta, (down/up)vote if you (dis/)agree.
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