"Thank you for not pushing."
Translation:Merci de ne pas pousser.
1) @https://www.duolingo.com/skill/fr/Verbs%3A-Infinitive, it says,"An infinitive can also modify a noun when used with de or à. It may take practice to decide which preposition should be used, but in general, use de whenever the infinitive has an object.". But the infinitive "pousser" doesnt have an object. Then why use DE. Why not "à"?
2) I have come across sentences where only "pas" is used and not,"ne...pas". When do you do that. Why not,"merci de pas pousser."
1) As mentioned in the Tips&Notes, there is no absolute rule of thumb to determine which preposition will be used. Picking "de" when the infinitive has an object is one tip. This does not mean that when the verb does not have an object, the preposition cannot be "de".
As you may remember, "merci" uses "de" with infinitives and "pour" or "de" with nouns.
- merci de ne pas pousser
- merci de/pour ton invitation.
2) In proper French and anyway in writing, negatives always need "ne". In spoken French, "ne" is often dropped because "pas, plus, jamais, rien, aucun, personne" are explicit enough to mean that the sentence is negative.
It's the English construction that I find ambiguous. I see it as a reference to something you have recently not done, though this might more accurately be represented by Thank you for having not pushed. I suppose I see Thank you for not pushing as an immediate past, along the lines of have just. It's hard to express, but it just does not seem to be present tense to me. It's rather like signs saying Thank you for not smoking, which, again, I translate in my head as Thank you for having not smoked. It's a construction I see occasionally in Britain, but not very often. I wonder if it is more common elsewhere in the English-speaking world? What's wrong with Please do not push, Please do not smoke? At least these maintain politeness and some economy and do not quite descend to the naked commands of Don't push!, Don't smoke!. Perhaps avoidance of the imperative was the motivation behind Thank you for not...
I don't agree because this can be a (pre-)warning or a piece of advice before any pushing has been done.
Remember that the formula "merci de (ne pas) + infinitive" means "please( do not) + verb".
On French trains, at the arrival, you can hear "Merci de ne rien oublier et de ne rien laisser dans le train. Des poubelles sont à votre disposition sur les quais." = Please do not leave anything on the train. Trash cans are at your disposal on the platforms.
On some forms you can read: "Merci de laisser cet espace en blanc" = Please leave this space blank.