Spanish language Q&A Forum

I have seen a lot of sentences like the examples below:

1. Todavía no han llegado, su avión debe haberse retrasado.

They haven't arrived yet, their flight must have had a delay.

2. Cristina ha debido de ser una buena profesora, sus estudiantes le han comprado flores.

Cristina must have been a good teacher, her students bought her some flowers.

I respect that Spanish uses punctuation differently, in some cases, from the way English uses punctuation.  However, the Spanish sentences and the English translations use a comma to separate the two sentences in each example (these examples were taken from a quiz on Kwiziq).  For the Spanish, I've checked RAE and I cannot understand why these two sentences are joined by a comma when it seems they should be separated by a period or a semicolon (or even possibly adding a connector or conjunction to join them).  For the English translation, in American English we would have to somehow separate these two complete sentences with some form of punctuation (period or semicolon).  I have also seen similar constructions in other writing, but not usually in newspapers or academic writing.  If you could provide an explanation, I would appreciate it. Thank you.

Hola,

Una de las personajes del programa española que veo dice lo siguiente:

"A ti se te da muy bien coser."  

¿Qué significa?  En este caso, "te" es un ejemplo del dativo del interés, ¿verdad? ¿A quién es conjugado "darse"? Al final, ¿hay una lección sobre esta construcción?

Muchas gracias

Ella se mudó allí hace dos meses.   Is this correct?  The lesson says we can't use the preterite with hace + time.

asi que un paraguas y muchos paraguas es igual?

Hi there, in this lesson there are a couple of errors,

In the introduction the sentence "This affects to all subjects" is a little confusing, I think that the "to" has found it's way in.
Secondly, there is no mention of the removal of the letter "i" for the ellos conjugation of the verb. Both examples show that it is gone, but there isn't a note in the lesson.
Thanks

Creo que la mujer no dice bien el "ir" de Irlanda.

In the sample question "Cuando vuelva Carlos, dile que quiero hablar con él." why is "quiero" not in the subjunctive tense? Didn't we learn in a different lesson than if a verb comes after 'que' that switches subject that it should be subjunctive? 

In a question requiring the answer "Sevilla es una de las ciudades más bonitas de España" I put en instead of de and was marked incorrect. However, as the lesson states, this isn't incorrect but simply 'less common'. In fact, isn't it so that a closer translation of the 'de' here might be '...one of the most beautiful Spanish cities' rather than '...cities in Spain'?

Here in Puerto Rico, it was suggested to me that one had the flavor of "perhaps" and the other "maybe", but I always forget which is which. 

Why does the accent change from comprárselos to cómpreselos depending on the conjugation? Does the stressed syllable always change in the imperative form?