If you include an image in an answer, you can specify the alt text of the image in brackets. In some posts, the image is an integral part of the answer, in which case the alt text is essential. Examples are "Are there police in the Wizarding World?" (with a poster from the Harry Potter movie shown as evidence) or "Why did Harry name his child after Snape?" (with Twitter posts).
This is all great, but there's a problem. The alt text is not searchable by the search box. (Also, very often, external search engines like Google prefer not to search in the alt text either, probably to avoid certain misuses of text that is often invisible.) Thus, such answers are difficult to search for.
When this is the case, I can work around the search problem by including the transcription or description of the image not only as the alt text, but also as plain text content under the image. I can certainly do this in my posts, but should I also edit other posters' posts this way when it seems useful?