Thank you. I think that is good practice to introduce abbreviations correctly. Even that it is easy to forget when you work with them all the time.

"How do I introduce an abbreviation in the text? The first time you use an abbreviation in the text, present both the spelled-out version and the short form." https://blog.apastyle.org/apastyle/abbreviations/

Or, you know, actually use HTML with the <abbr> tag ...

Yep, especially when they are not general purpose like "PC" but from a very specific knowledge area. In this case it's even an old one. New engineers won't be educated to do ETL anymore.

Yes, its poor writing/editing of articles that don't define their acronyms. or at least the important ones in the title.