I am the "commenter" that you're referring to in the last sentence. Before explaining anything, I would like to draw your attention to the benefits of having things properly typed.
More efficient (math) searching
We can easily find a bunch of questions with math expressions like "$n < 2^n$" with the help of Approach0.
Figure 1: Logo of the math search engine Approach0
Image source: Approach0's GitHub profile
Figure 2: Approach0 search for "$n < 2^n$" with "induction".
Figure 3: corresponding Approach0's search results
As we can see from Figure 3, the matched expressions get $\bbox[yellow, 1pt]{\textit{highlighted}}$, notably "$\bbox[yellow, 1pt]{\textit{induction}}$" and "$\bbox[yellow, 1pt]{n < 2^n}$". Moreover, it can also $\bbox[yellow, 1pt]{\textit{highlight}}$ "$\bbox[yellow, 1pt]{k < 2^k}$". That's not something that usual web search engines (including the built-in one on SE) would do. This helps the community to spot out possible duplicates despite difference in the choice of variables.
Improved accessibility
People with disabilities have been contributing to our communities, we shouldn't exclude them from participating in the SE network, which favors a "be nice" policy.
Figure 4: A visually impaired person using a screen reader
Image source: YouTube
Unluckily, text images (image files whose content is text) pose technical difficulties to screen readers. Thus, text images hinder those using screen readers, such as the visually impaired, persons suffered from reading and writing disorder, from participating in SE.
As the name "Stack Exchange" suggests, this network promotes and facilitates the exchange of ideas between individuals. In the next section, you're going to see why SE's moderators are against the use of text images.
Despite Euler's blindness, he had been contributing to the math that we're now using. While making use of the math that disabled persons have contributed to, should we stop disabled persons from reading our posts?
Figure 5: Leonhard Euler
Image source: Wikipedia
SEO friendly
"Google Does Not Extract Text from Images"
(Image) source: Did Google Just Read the Text on My Image and Can This Affect My Rankings? by Razvan Gavrilas
If everything has been typed out, then a web search engine can interpret its content. Compare these two version of the question in terms of SEO:
- Original version of the main site question
- Typed out in $\rm \LaTeX$ by @TheSimpliFire.
Google sees an image by its alt attribute. In your main site question, it's "image", which is not descriptive. Therefore, your image alone can hardly be useful to the search engine. In general, it's advised to give descriptive alt text to a web image.
From the previous comparison, it's clear why SE moderators and staff prefer users to "type everything out".
My response to your remarks
For me it is such a misproportion of a harsh comment to a small question that I thought to simply self-delete the question and just take the given hints with me.
(Edited in response to @TBonger's comment)
I began with "please", and provided links to relevant meta posts for further info. I can hardly see any harshness in my comments.
I've misused the word "forbidden" in my comment. There's no mechanism stopping the upload of text images on SE. I should have said "discouraged" instead. My apologies for OP.
The system-self-deleting-apparatus reminded me of disadvantages of such self-deleting of question once answers (and work of other members) are/is involved.
In general, one should never self-delete his/her own question after receiving an answer. In particular, on Math.SE, it's OK to self-delete his/her own question only if the only existing answer is a non-mathematical one.
For your question, you have received more than one answer, so the system won't let you self-delete your own answer to avoid content loss of the site.
So I ask here: what to do best?
The linked Meta.SE answer has already answered it.
"Type everything out, so it is all searchable."
Hiding your image from display while leaving the link doesn't improve the clarity of your question. As other users point out, that's even worse: that can't help users using screen readers, but that also hinders normal users from viewing the content. As one of my links in my comments to your main site question suggests, your question should "contain sufficient context to be answered without the external context" (i.e. the screenshot of your PDF).
Remarks: No matter your text image is a from a book/a PDF, no matter it is scanned or screen captured, the idea of SEO-friendliness still applies.
