Weak Interruptions

Question

What is a weak interruption and more importantly, how do I recognize it?

According to the page below, these are weak interruptions

If the break is weak, do not use comma(s).

Anna called to say her car would not start. Rafael will therefore have to walk to school.

Weak interruption = no commas.

The long noodles splashed tomato sauce all over the front of Brenda's shirt. Ordering fettuccine was a mistake indeed.

Weak interruption = no comma.

How is the interruption below from the same page different from the above?

After mowing the yard in the hot sun, Pedro was too hungry to shower. He did wash his dusty hands, however.

I do not think you make weak or strong interruption simply by removing or adding a comma.

Note: I read on another website that a weak interruption is a non-restrictive clause, or non-essential information. The examples above, however, do not show any clauses of that sort.

Source: The Conjunctive Adverb. Recognize a conjunctive adverb when you see one

Answer 1

Commas simply mirror the way a sentence might be spoken out loud. What your text calls a "strong interruption" simply means that there would be a pause between one word and the next, to indicate a change in the direction of conversation. In most of these cases this is up to individual style to decide whether to pause or not.

Both of these are correct:

She told me she was not friends with him, but I'm pretty sure I saw her talking to him, outside the cafeteria.

She told me she was not friends with him but I'm pretty sure I saw her talking to him outside the cafeteria.

Commas often serve no function other than to make a sentence easier to read.