The majority of the words that you have written in bold are a type of adverbial (a type of adverb) which is called an disjunct. (whether they are all disjuncts could be argued.).
.Disjuncts allow the speaker/writer to influence the hearer or reader.. They represent the speaker's attitude about what he is going to say.
Here are some examples where the adjunct is written in bold:
Naturally, you are going to go you. = the speaker is certain you will go.
Obviously,I agree with the president. = Its obvious that the speaker will agree.
Of course, she is late. = I think it is to be expected.
Regrettably, he didn't attend the meeting.= I think its sad or too bad that he didn't come.
Surely, you are going to go to school today. = a strong sense of persuasion.
Frankly, I couldn't care less about comma rules. = the speaker really doesn't care.
In each case we use a comma to separate the emotion or attitude of the speaker from the rest of the sentence. Some authorities believe that a comma should be used if the disjunct doesn't flow with the rest of the sentence and in most cases disjuncts are separated by a comma.
There are no hard and fast rules about comma use. and convention plays a role in determining some rules. You learn from experience and even English teachers can get it wrong.
Source Grammar 33 manual U of Saskatchewan, Longman's Dictionary, Guide to Grammar Writing by Charles Darling.