I don't know if it's just me, feel free to ignore my feedback, but the article feels a bit random in terms of overall structure.
Here are the parts that confused me the most:
Now, it's time to lay our cards on the table and tell you what solutions we had in mind.
Solutions for what? Generic "challenges"? And whatever follows in this section doesn't really seem too related to custom programming languages, other than the PHP reference (but I'm not sure how mentioning that solves anything, or why you would put it into that section).
Today, we'll share our experience, which may inspire you to enhance your expertise. What gives rise to expertise in programming?
Wasn't the article about making a programming language? That seems mostly unrelated to generic expertise in programming. Story #1, #2, #3 in the top section seem unrelated too.
What does expertise mean for PVS-Studio?
What expertise, in making custom programming languages? The section seems to be about something else, an analyzer and diagnostics. I understand those could be in some situations considered related, but there seems no motivation given why you would think they are here. So it feels a bit disjointed.
Revealing secrets
About what, making a custom programming language? Nothing that comes right after seems an actual secret, let alone one relevant for custom programming languages.
It might be just me being a bit dense. However, I can't shake the feeling that this article could have worked better if cut down to less than a quarter of the length, and with some more focus on a clear topic.