Reading the KH rules, these are the only two cases when we can place a rift marker (not a rift progress marker) on a rift track:
1 - at the start of the game: "At the start of the game, the three rifts are closed, and the corresponding rift markers are placed randomly on the three Rift Tracks on the Kingsport board to show this."
2 - when a rift has been closed: "Once all four rift progress markers associated with an open rift have been turned facedown, the rift closes; the rift marker is returned to its Rift Track and the four rift progress markers are discarded to their pile."

This Kingsport Horror Mythos card 'Worlds Drifting Apart' says: "While this card is in play, no RIFT TOKENS may be placed on the rift track."
I missed something here. In the KH rules I find only "rift markers" or "rift progress markers". Maybe a "rift progress marker" is a "rift token"?
Otherwise, since the card title is "Worlds Drifting Apart", it should be: "While this card is in play, no RIFT PROGRESS MARKERS may be placed on A rift track". It would have more sense.

What do you think about the text on this card?

It is refering to the Rift Progress Markers. The mythos card effectively freezes the rift track.

Is this the same with the Mythos card "Strange Visions Cease" ?
It says: "The first player chooses one rift token on the rift track. If that rift is active, turn the token facedown. Otherwise, return it to the bank."

It is speaking about "rift progress marker", isn't it ?

Yes. Tokens/markers/whatever will be the smaller bits. The others are the actual "Rifts."