How doesn't a comma between a long subject and verb, improve readability?

Question

Source: Rebecca Gowers. Plain Words (2014 ed). p. 247 Middle.

Foreword: The title instances one such use of the comma.

(6) The use of a comma to mark the end of the subject of a verb, or the beginning of the object. (See also chapter 9.1.)

It cannot be said to be always wrong to use a comma to mark the end of a composite subject, because good writers sometimes do it deliberately. For instance, one might write:

The question whether it is legitimate to use a comma to mark the end of the subject, is an arguable one.

But the comma is unnecessary; the reader does not need its help.

But am I the only one who judge such commas to help separate a lengthy subject from its verb? Otherwise I'd need reread the sentence thrice. p. 175 Top of Legal Writing in Plain English (2013 2 ed.) agrees with Gowers:

1.8. Don’t use a comma between a subject and its verb.

The use of the terms “irrebuttable presumption” and “conclusive presumption,” should be discontinued as useless and confusing.

An insurance carrier or a union or union inspector, may be held liable under traditional tort concepts for the negligent performance of such an inspection.

Answer 1

Gowers explains this correctly.

The use of a comma is to improve readability. Some writers put a comma after a long subject on purpose, but generally it doesn't help.

If you reach a comma after a subject you will start trying to process the sentence in one of two ways. Either the subject phrase was actually a participle phrase, or the part following the comma is a parenthetical insertion.

So you reach the verb, and you try to understand this as parenthetical phrase, this fails so you back-track. Was the first part of the sentence a participle phrase or an adverbial or something else, you re-read it and finally fall back to interpreting it as a complex subject followed by a comma. Then you can parse the sentence correctly.

As Gowers notes, "The comma is unnecessary; the reader doesn't require its help." And when something is unnecessary, you should leave it out.

However when a comma reduces confusion it should be inserted. For example, in "What he thought it was, was not clear", where the comma separates two tokens of the same verb. And in "Most of those who can, work at home", where it prevents at home being taken as complement of can. – BillJ

Answer 2

It doesn't.

Personally, when reading English, I've always been rather ticked off by those commas in the middle of sentences. They're unnecessary, they kill the flow of the writing, and I think there are better ways of indicating the subject in a sentence. As the reader, if I see that comma when reading, the voice in my head inserts a little pause in the sentence, then my brain realises that that pause is wrong, and I lose momentum due to the ensuing confusion.

The question whether it is legitimate to use a comma to mark the end of the subject, is an arguable one.

If I really wanted to make sure the reader knew what the subject was, I'd write:

The question - whether it is legitimate to use a comma to mark the end of the subject - is an arguable one.

or with a bit of a twist,

The legitimacy of the use of a comma marking the end of the subject is an hotly-contested topic.

There are lots of ways to communicate this idea clearly, one of which is simply removing the comma entirely.

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My own spin on the question's title:

When placed between a long subject and verb, does a comma detract from readability?