According to its profile, the community user randomly pokes old unanswered questions every hour to get them some attention. What does this poke consist of? Is it an action ordinary users are theoretically capable of, or is it some special internal thing like updating the modification timestamp directly?
The poke consists of essentially nothing. It is a 'modification' of the thread that does not modify anything visible. The sole effect is that the question gets a new last modified time (by Community) and thus is put at the top of the active list, giving it visibility.
A user cannot do this in this way. A user could 'fake' this via modifying the thread in some insubstantive way such as a trivial edit or post and delete an answer. But, a user rather should not do this. If a user wants to give anew visibility to a qustion the standard way to do this is via a bounty.
Tangentially, but since it sometimes is misunderstood: not all questions without answer are eligible for poking. In fact only (certain) questions with answer yet still in the 'unanaswered' list are eligible.