The word rather is common in everyday situations, having several meanings and applications that native English speakers take for granted. In writing, however, using rather causes some concern because of uncertainty regarding the placement of associated commas. The main thing to remember is that “rather” almost never takes a comma, but when it does, the comma is most often one of a pair that serves to set something apart and make it nonessential (hence, parenthetical) to the core meaning of the sentence. Finding rather attached to a single comma is rather rare.
When rather's not essential,
Two commas separate it;
And comma unilateral
Is never there permitted.
It's parenthetically
Diverting us with data
That's not required really,
A smoothish operator.
“One doesn't wish to linger
But, rather, keep on going.
The time to rest is yonder
When past the area daring.”
A single comma seldom
With safety is abounding,
And “rather” feels more winsome
With commas—two—attending.
So, “rather,” almost certain,
Eschews a single comma,
Unless conjunctive curtain
It hangs before the comma.
In being conjunctive adverb,
Connective function serving,
It joins two parts that contrast
Across a stop or such thing;
A semicolon often,
The bridge for many takers,
To “rather” then will shunt them,
Suggesting comma spacer.
“Let's not hold on to doubting
Forever; rather, let us
Advance with faith, asserting
That grace removes all onus.”
But when a simple adverb,
With meaning only “fairly,”
Or when it tells of preference,
Degree, or if exactly,
Or “rather than“ in complex
(With words between or after),
No comma leads and ushers
That “rather” in its barter.
“I'd rather peel an apple
Than juice a yellow lemon;
Get flavor rather subtle,
Not rather tempt a demon.”