Punctuation around the word "namely"

It seems somehow tricky to apply the right punctuation when it comes to the word namely. I got the following advice:

Search globally for "namely", and add a comma after it, as well as a comma, a semicolon, or a period before.

On the other hand, this link and this one suggest that there might be more to consider. So, what are the rules for punctuating around the word namely? Please try to prove your claims by including references.

I don't think that any settled and widely accepted rule for handling "namely" exists, which makes the challenge to "prove your claims by including references" rather difficult. The link you provide to Merriam-Webster's Learner's Dictionary is useful because it describes some of the numerous ways that people deal with "namely," including these:

—namely,

—namely [no back punctuation]

, namely,

, namely [no back punctuation]

But that source doesn't account for other possibilities, such as these:

(namely,

(namely [no back punctuation]

; namely,

; namely [no back punctuation]

: namely,

: namely [no back punctuation]

. Namely,

. Namely [no back punctuation]

As the contrasting comments and responses to your question indicate, people have very different preferences for punctuating "namely." I favor the —namely, option, which I like because it establishes a clean break from the wording responsible for the deficiency in identification that the words following "namely" are dedicated to supplying. Nevertheless, I can't claim that my preference is anything more than a preference.