Yes, its done in most eukaryotes.

It does exist in nature and mechanisms of RNA interference are pretty well understood. The headline is actually incorrect here as the gene isn't altered, but instead the RNA product of the gene is suppressed.

The important thing for safety is that this works at the level of RNA rather than by modifying DNA (which is how things like CRISPR work). Actions at the RNA level are effectively reversible; once the interfering RNA degrades the effect will go away. On this basis you can predict that it's unlikely to have many deleterious long-term effects, although you should still do trials to check.