Is it acceptable to include footnotes in mathematical proofs? When writing a technical article that includes mathematical proofs: Is it acceptable to have footnotes within the body of a formal proof (to elaborate/clarify non-essential points) or is the use of footnotes in proofs considered bad practice?
Like almost anything else in writing, style should follow function. In other words, if you think that a footnote makes it easier for your reader to follow a text (for example, because it explains an aside that is too long for a parenthetical remark), then it is appropriate to use one. There is no general guideline whether footnotes are acceptable or not. It all depends on what you want to say and how you want to say it -- choose whatever means you think are appropriate to tell the story of the proof.