As mentioned before, my interests in conlanging and Doctor Who don't overlap as much as I'd like, due to Tardis telepathically translating everything. This apparently goes for writing too - in The Impossible Planet the Doctor realises that they're in a particularly dangerous situation when they encounter a script that the Tardis can't translate.
However, something odd has been going on this season. Amidst the rumours of the Hybrid, the theme of Truth of Consequences, the story of Ashildr, and the build up to the death of Clara, there's been another, more subtle theme in the background. In Under the Lake / Before the Flood, the Fisher King scratches this on the wall of his hearse.
The Doctor can't read it, and has to get Cass to lip-read what the ghosts are saying before he can work out what it means. The reason that the Tardis can't translate it is that the writing is intended to plant a message in the mind of the reader. Also, in that story we have the use of British Sign Language, which the Tardis can't translate because The Doctor's forgotten it.
In The Zygon Invasion / The Zygon Inversion we see this where the Zygon rebels have been active.
Neither The Doctor, Clara nor the Tardis is present in these scenes, and whatever the poster says doesn't come into the story.
In this case it's not translated because what we're seeing has been hacked from the visual cortices of those who experienced the events, most of whom could read the script to start with. As in Under the Lake / Before the Flood, Ramussen's broadcast is meant to be a vector for mental malware.
Finally, in Face the Raven, we get this.
This is a bit of an oddity. It's the Aurebesh script from Star Wars, which is simply a cipher for the Roman alphabet (Star Wars never having cared about plausible languages). It says Delorean, which is presumably a Back to the Future reference. It looks like this is just an in-joke.
So, is this leading up to something? Might Doctor Who be about to start using conlangs? And if so, please can I make one?