It is against the rules. Rules which you probably have not read. Depending on the case one could classify it as thread hijacking.
I have read "the rules".
This version:
https://bitcointalk.org/index.php?topic=994018.0There is nothing similar to "thread hijacking" and talking about bitcoin accepting digital services "in other's thread".
In what part of the rules is about "thread hijacking"?
If the thread is not in the "Marketplace", talking about various services help to bitcoin users for better money management and encrise the value of Bitcoin in real services.