People should be encouraged to avoid putting the main content of their question in an image. This makes the question harder to find using search and inaccessible to the visually impaired, which is less than ideal. Making something harder to find via search is especially unfortunate, as it means that others who might be interested in the same question won't be able to benefit from the answers and knowledge accumulated here. It's also bad for the site, as it means the site loses a chance to attract new users through Google search.
Instead, people should be encouraged to transcribe text and mathematics themselves, using LaTeX as appropriate.
As another reminder: people should be reminded to give proper attribution to all sources, when appropriate. I've noticed that it's common for such images to be a screenshot or scan of a textbook, lecture notes, or other source that is not written by the original poster. In these cases, it is important to provide attribution in the question to credit the original source of the material, as plagiarism is problematic on this site.
Here is a template for an example comment you can leave for the poster in these situations, if you deem it appropriate:
Don't use images as main content of your post. This makes your question impossible to search and inaccessible to the visually impaired. Please transcribe text and mathematics (note that you can [use LaTeX](https://math.meta.stackexchange.com/q/5020/)) and don't forget to give proper attribution to your sources.
Don't use images as main content of your post. This makes your question impossible to search and inaccessible to the visually impaired. Please transcribe text and mathematics (note that you can use LaTeX) and don't forget to give proper attribution to your sources.
For reference, you can find similar discussion on the network-side Meta site: How to handle images containing text (vs text)? and Allowed to post scanned page from text book on SE and Using (only) scan/photograph/screenshot of text as an answer?. The conclusions there are similar. On this site, On the inclusion of pages-of-text-as-images in questions and Are pictures of hand-written drawings allowed are related and helpful as well.