Why do people say putting a "." (full stop) inside "" quote marks is grammatically correct/right?

Question

The question I'm asking is why people put a "." (full stop) inside "" quote marks, why is this grammatically correct/right for English?

From my computer coding knowledge, I think the quoted text - coding: (literal) string sequence of characters - is a different phrase to the sentence outside of it and that sentence it's in needs to be closed with a full stop, not the quote. People don't say things ending with "." - "Hello.".

I don't understand why punctuation and grammar correction in virtual keyboards on mobile devices (phone, tablet, some laptops) wants to use this... why is this grammatically correct/right for writing with English?

Answer 1

Why? For historical reasons. English orthography was not created according to logical principles, but has slowly developed over hundreds of years of usage. Eventually a certain usage became the predominant convention and has finally been codified as rules.

I could retell for you the historical development of the placement of the full stop in relation to quotation marks up to the present. But that seems irrelevant (and off topic) in the context of writing. You could ask about that on https://english.stackexchange.com or https://linguistics.stackexchange.com.

More important (for writing) is the fact that the rule you quote is not universal. There is a difference between British and American usage, for example, and between wether what is inside the quotation marks is a full sentence or not:

Monica told him about "that guy." (American English)
Monica told him about "that guy". (British English)
Monica said, "I like that guy." (both British and American English)

It is also important to note that different style guides may recommend a different placement of the full stop. For example, the (American) Chicago Manual of Style recommends the "British style" (full stop outside quotation marks) whenever the sentence might become ambivalent otherwise.