From Wikipedia:

The party was cofounded on 24 November 2012 by Birgitta Jónsdóttir (previously a member of the Movement), and several prominent Internet activists, including Smári McCarthy. The party successfully applied for the ballot list letter Þ (resembling the party's logo) in order to run in the 2013. In July 2016 the party requested and was issued the letter P for future elections.

I thought it was nice how they officially used the letter Þ. What are the publicly stated reasons to switch to the (more conventional) letter P?