When Pluto transits natal Mercury, the intensity is mind-boggling. It’s like any other Pluto transit. The effects are deep and it can a long to assimilate what come to the surface.
You’re likely to experience a communication (Mercury) blackout (Pluto). This might happen because you shut down. In other cases, you may be shut out. What you say repulses people – they drop you.
You’ll have a lot of insight, though. Possibly more than you’d prefer. Perceiving other people’s underpinnings isn’t necessarily pleasant, never mind. encountering your own taboo thoughts. There’s little relief with this transit and it can manifest as paranoia.
It’s also common to focus on something and read all about it. For example, a person could learn astrology during a Pluto transit to Mercury. You’re likely to be drawn to darker topics though, and may very well become obsessed.
What happened when Pluto squared your Mercury?