Yes, I know it was cloudy because I didn’t want to confuse you by adding another topic. What happens is that there are expressions such as this:
It’s something like “I can’t believe that he didn’t even greet me”. It shows regret, sadness, blame, …
As I said, this is a special set expression, separate from the general rule of using infinitive to use a verb as a subject in the sentence.
Both variations “ni yo podría/pudiera” mean the exact same thing. In principle, it should be a conditional (“podría”) because you use this form for main clauses and “pudiera” mostly for subordinate on, for example:
Yo podría hacerlo si él pudiera ayudarme.
In contrast, this would sound a bit old-fashioned/dialectal, at least to my ears, although it’s not incorrect:
However, it is possible to use the “pudiera” form instead of “podría”. Nowadays it sounds a bit old-fashioned (at least in my way of speaking). For the “pluscuamperfecto” form, on the other hand, it’s absolutely normal to replace “habría hecho”, and so on, with “hubiera hecho” (but not the other way around). E.g.
Lo habría hecho si hubiera podido
Lo hubiera hecho si hubiera podido
are both possible and frequent.
Some of my examples do use infinitives at the beginning of the sentence and it’s quite possible and frequent.
As for infinitives instead of imperatives, this is a bit complex because there are differnt tendencies.
First, using a “real” infinitive in a positive command is, as you point out, a bit formal. It is used for instructions: cooking recipes, formal instructions in signs and so on, as you mention, …
On the other hand, negative infinitives as a command are more frequent and less formal.
It still sounds as if it had been written but it could be an informal sign, for example.
However, there’s another phenomenon which makes “fake infinitives” very frequent to express commands. This is possibly unique to Spain. As you know many speakers (not all!) in Spain use “vosotros/as” instead of “ustedes” when addressing people they know. The imperative form for “vosotros” end in “d”
Well, colloquially it is very usual for people to change the “d” into “r” and pronounce it as if it were an infinitive:
When there are pronouns the correct form would me:
But you hear “callaros” very often.
In some areas speakers even use the negative form:
Those forms sound vulgar, the last one even more than the previous ones but you can hear them, and the first two very often, to the point that the “Real Academia” has recently accepted them as colloquial variants.
Notice that all the cases refer to several people, never to one single person. Even the example of formal instructions addresses more than one person, at least implicitly.
In your example it is the “si” part that makes it impossible to understand “corregirme” as an infinitive, so the imperative is the only possible interpretation. Consider a literal translation into English:
Notice that it doesn’t make sense in English as a complete sentence, either, whereas
would be awkward in English but it does make sense.
The “para” is correct but the sentence should be:
It’s simply a bit awkward for everyday conversation but it is not incorrect. It may be used in a song to keep the rhyme, for example.
and this is an english question why does this sound horrible to me It is necessary to correct me and this sounds natural > correct me if it is necessary?
I think English only uses “it is necessary” for absolute, universal rules and it sounds awkward if you express a suggestion that way. It seems to be a rather formal, stilted way of speaking as well.
In Spanish “es necesario” also sounds too formal for many situations. English prefers to use “you” in informal conversation to express general statements or rules, rather than impersonal expressions, such as “it is necessary”. This is true even when “you” doesn’t refer to anyone in particular:
In Spanish, in contrast, impersonal expressions are more common in informal speech:
[I’ve added an example of “ni” in the sense of “not even”.]
Another common impersonal expression is “hay que”
Informal English would, once again, prefer an “impersonal you”