Understand your frustration with how I've communicated my position, sorry about that:

My justification for the examples I've given is there still needs to be other context, is based on complexity of the equation, and the intended audience of that equation.

An example of me not explaining a very simple equation would be perhaps a table of various cases:

|

| mass flow (kg/hr) | density (kg/m³) | Volumetric flow (m³/hr), V = m/ρ | | Case 1 | blah blah | blah blah | blah | | Etc. | ... | ... | ... |

Realising now that markdown tables don't seem to work 😅, hopefully this is still clear.

It may be a touch better to put variable symbols in the other columns, but:

1. You still have the final answer (the purpose of my report, I'm not writing a thesis here)
2. It should be plainly obvious by the units, and the fact those are the previous two variables, to someone who has the ability to understand (and is the intended audience of that little equation)

As a recent example for this, in a data sheet I recently prepared, I literally just put a * in the references column and said "*calculated from other data sheet values" for the volumetric flow rate, because the intended audience would know how to do that, and the purpose was for me to communicate how that value was determined.

Me putting in the V = m/ρ in the hypothetical example I gave above is a just a little mind jog for the reader.

Where more complicated equations are used, of course these are properly referenced, usually even with the standard or book it's come from.

I'll redefine my position to: Clearly define all variables, unless it's abundantly obvious to your intended audience from context.

My intended audience of the conclusions or final values are the layman. My intended audience of everything else is someone with a very basic chemical engineering understanding.

Your last point is a strawman:

I find it a bit contradicting to the very point you made about defining variables. If anything, one might be some home-grown genius that has real business getting into details but only ever used Chinese characters as variables

Because I'm writing in English, for an English speaking audience, and there is no such thing as a home-grown genius getting into my area because it's a legal requirement that they have an honours degree. Even still, the two assumed knowledge equations I mentioned, which I would only not reference with sufficient context, would STILL be recognisable with totally random symbols.

| mass flow (kg/hr) | density (kg/m³) | Volumetric flow (m³/hr), 容 = 质/密 | Yup, a bit odd in an English context, but with the units information (always mandatory, of course) completely understandable.