I became confused by comments to my answer insisting that Technical writing is jargon using incorrect English words.

I also looked through definitions of "prepend" in internet, all with inserted derogatory remarks, even in IT-specialized dictionaries, like 'jargon' and:

• prepend is not an English word. It was created to sound like the opposite of "append," which means to add to the end. The correct English word is "prefix;
• Although it sounds correct, prepend is not an English word. It was created to sound like the opposite of "append," which means to add to the end. The correct English word is "prefix;" for example,

Is Technical Writing jargon or writing-style and the branch of correctly used English?
Would I better avoid to refer to it as English at all while copywriting (or copylefting) in it?

Update:
If I write using the words which are not English WORDS, do I write in English?

Update2:

I've read many definitions of copywriting but basically it is to poularize a product or a point of view to a most general (including illiterate) reader. The term Copywriting "refers to writing in the sense of creating non-technical material". Where is here a "jargon is nearly impossible for the average person to decipher", given by all answers, I wonder?

Update3:
Some of jargon definitions:

• Jargon (JAR´gen) - Meaningless use of words
• The technical language of a particular group that is inappropriate in most formal writing since it is frequently not understandable by those outside the group

What is unclear in "prepend" and to whom?
Why isn't busyness letter or step-by-step instructions a formal writing?