For the record, I appreciate you sticking around to defend yourself. Upvoted for that and no ill will here.
But even according to the 'rules', idiosyncratic is an adjective. If it only described human actions, it would be strictly an adverb.
The first example given in a google search for idiosyncratic is, "she emerged as one of the great, idiosyncratic talents of the nineties".
This usage is not describing actions but rather a subject, a noun- In this case, a person.
It describes the subject as idiosyncratic, not their actions but the subject itself.
Merriam-Webster further defines the word as an individualizing characteristic of temperament or constitution.
Constitution referring to the general 'composition of something.'
If there is an outlier to the 'general composition of something', it can be accurately referred to as idiosyncratic.
For instance, an allied soldier wearing a longsword and bagpipes into battle (Jack Churchill) can be aptly described as wearing an idiosyncratic uniform and gear. Likewise, his temperament and actions can also be described as idiosyncratic (your strict definition).
This is also why idiosyncrasy is a common medical term used to describe things which are not usual or expected.
"She presented idiosyncratic symptoms not usual to appendicitis."
When you said, "I can put it very simply idiosyncratic is a word used to describe a persons actions, not a photo", you were simply wrong.
If I have a collage of war photos, all of which feature standard issue soldier uniforms, with one photo of a soldier wearing a bunny costume standing next to a bear with a bottle of vodka in its claws, you can absolutely and correctly describe this particular photo as 'idiosyncratic'.
It is 'peculiar' and an 'individualizing characteristic' of the 'general composition of something'.
This isn't even playing fast and loose with organic language, this is the definition of the word.
You might have an argument for embezzle, because it has a stricter modern usage usually applied to judicial terminology, but the actual definition of the word does not strictly apply to financial law.
It comes from a word meaning to 'destroy or make away with'. A break-down for this word is 'misuse' or 'hide as', meaning you are misusing or hiding something and presenting it as something else.
In this case people are hiding their overused jokes as actual discussions about upcoming content. I could have also used the word 'smuggle', which has a strict legal definition, but also means to conceal and import something. Import can mean to traffic across borders, or present or manifest something from a different source.
Yes, embezzle has a legal definition, and it has other definitions, connotations and denotations.
For instance and as another example: In jurisprudence an 'affair' is a lawsuit, in general language it means to bang your neighbor.
An 'annex' is an addendum to a legal document. In most common usage it refers to a building.
Basically both of those words are used correctly, and if you're going to try to flex on the semantic usage of words and call someone out for not using them properly, which is like I said before basically the entire reason a sub dedicated to beingverysmart exists, check those words out before.