Punctuation

The hotel,since,it opened has become very popular.

The hotel, since it opened, has become very popular.

The hotel, since it opened, has become very popular.

The hotel, since it opened, has become very popular.

Commas used in this way are called parenthesis. It can be used to separate parts of a sentence  (i.e., additional information that is not essential to making the sentence make sense).  This can be done using dashes or brackets too!Here are some examples: The fastest boat in the race, which won by 12 seconds, was Pembrokeshire. Mr  Millar, 36, was jailed for robbing his father's grocery store. James, a 23-year-old beggar from Hale, sold his 4-million-pound mansion.The hotel, since it has opened, has become very popular. The sentence also works as 'The hotel has become very popular.' so we can tell that 'since it has opened' is the extra information to put in parenthesis.

The hotel, since it opened, has become very popular. 

The hotel, since it opened, has become very popular. 

The hotel, since it opened, has become very popular. 

The commas are used here to add extra information, also known as parenthesis. Here we would add the commas in a way in which there is a comma before the extra information and one after the extra information. In this case the extra information would be ‘since it has opened’ because the sentence would also make sense as just ‘the hotel has become very popular’. This means that our sentence with the parenthesis would be: ‘the hotel, since it opened, has become very popular’.