Elon Musk had been in negotiations to acquire social media platform Twitter

[Ostap]

In "the social media platform, Twitter", the article and comma are omitted as an exception to the rule, as "Twitter" is all too well known as a social media platform.

What rule are you referring to? Adding a comma would make it incorrect in the original context.

 

[kadioguy]

[...]

What do you think about post #18?

 

[Ostap]

What do you think about post #18?

I'd agree with Tedmc that Manager Tom would be sort of a nickname, and "the" may or may not be part of it. But with a comma it would more likely ba a part of a sentence.

 

[kadioguy]

I'd say "Manager Tom", as in a nickname given to Tom. Or it is "the manager, Tom" (same as "Tom, the manager".
[...]

Is the "in" necessary?

And how about "I'd say 'Manager Tom' [no comma here] as a nickname given to Tom"?

 

[tedmc]

Is the "in" necessary?

And how about "I'd say 'Manager Tom' [no comma here] as a nickname given to Tom"?

You can do without "in" but there is a slight difference in meaning.

"As in" is a phrasal verb which means "which is" or "which means"

 

[kadioguy]

You can do without "in" but there is a slight difference in meaning.

"As in" is a phrasal verb which means "which is" or "which means"

1. I'd say 'Manager Tom', as in a nickname given to Tom.
2. I'd say 'Manager Tom' as a nickname given to Tom.
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For (1), please see:

The ‘h’ in honest is silent, as in ‘hour’. [Oxford]

So for your sentence, I'd say something like this (which makes more clear to me):

I'd say 'Manager Tom', as in a nickname 'Powerful Manager Tom' given to Tom.

When "X as in Y", that means X is part of Y. That's how I understand it.
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(Update)
Ah, I think that the structure of your sentence is more like this one:

Repeat these five steps, as in the last exercise. [Oxford]