Learn Russian: Журналист написал, что это якобы фейк. - The journalist wrote that this is supposedly a fake.

While both report what someone else said, якобы translates to "allegedly" or "supposedly" and strongly emphasizes that the speaker takes no responsibility for the claim, often implying doubt. It is very common in journalism. мол, on the other hand, is highly colloquial and acts more like verbal quotation marks (like saying "and he goes, 'it's a fake'").

Why aren't there commas around якобы here, the way there are for words like кажется?

In Russian grammar, якобы is classified as a particle, not an introductory word. Because of this, it is never set off by commas. It simply sits directly before the word it casts doubt on, which in this case is фейк.

In English, we would normally shift the tense and say "wrote that it WAS a fake." Why doesn't Russian do this?

Russian does not use the "sequence of tenses" rule found in English. Instead, the subordinate clause after что keeps the exact tense the person originally used in their own thoughts or words. Since the journalist thought "This IS a fake" (это фейк), the present tense is kept even though the main verb написал is in the past tense.

Is фейк a standard Russian word now, or just slang?