I’m afraid this will also be a non-answer to your question, but it may shed some light on how opinions vary, and show how one might see green where another sees blue.
I’ll start with a very localised problem, but hopefully it illustrates a greater truth.
There is a tendency in the last 15-20 years (or even longer, some could argue) in Quebec for some members of the elite to use a register that is openly and proudly familiar, which led in some cases to unfortunate and inappropriate messages being sent ‘officially’ by politicians or spokespersons of certain organisms.
An effect of having a non-negligeable proportion of people in high social position anchoring themselves deeply into the familiar register has been to give this type of sometimes rough-edged language a truthfullness that has now eroded the trust of some people towards someone whose language is too far remote from that of the streets.
On the other hand, this has ignited a very strong response from purists, turning things into a very polarized vision of how words and messages should be spoken and communicated.
Obviously, when things are polarized, there is more often than not little room for a cold analysis of the pros and cons of each side, because the extremes are very angry and scream louder than everybody else.
So we are into the case where opinions may vary between:
- Formal register is a sign of duplicity, and we better avoid it altogether; and...
- Even formal register is not good enough, and one should strive to enhance even grocerie lists.
And obviously, certain words and expressions will be labelled differently by the two extreme groups: « De toute évidence » could be perfectly natural for someone, and overly precious for someone else who would never even consider using it instead of « C’est bien évident que ». Most people, the ‘silent majority’, will have mild opinions on this type of issue, but obviously, every now and again, some expression will strike any hearer as too precious and somehow artificial or clearly despicable and offensive.
My way of reacting to either of these cases is usually to laugh and ask for explanations. This way, my first opinion is not a secret, and I allow the speaker to justify the choice of words. It practically never creates any tension. True though, not everyone will react the same. It might be good to look for signs of discomfort from your audience. But ultimately, the message you’re sending should be much more powerful than the way you’re transmitting it, so unless you really try to create a reaction or to chance some lyrical poetry, people should react mostly to the content of your message, not to its container.
Also, I do not believe it is the task of a dictionary to overly fine-tune the registers to which words belong. When a dictionary calls Formal, it is only really About formal, or Most of the time formal. Writers and poets have been playing with registers and blending them with a lot of success, to emphasize, to create humour, to stylize and give a vibrant feel to a text, or to fulfill a lot of different purposes, so being picky on slight variations of language to me is overkill.
To finish this in beauty and smile, to counterweight the absence of clear answer, I’ll leave the last line to a classic example (attributed to the French Academy member Jacques de Lacretelle, thanks Laure) of a very classy and perfectly used imparfait du subjonctif with a very low, classless word to finish the sentence, proof that popular and literary tones can quite happily coexist in a single sentence.
- Il m’eut déplu que vous m’imputassiez cette connerie.