The user might also want to know about the episode's significance and themes. Episode 590 deals with themes of freedom, humanity vs. beastiality, and the struggle of the Fishman characters. Highlighting character development in characters like Brook, Chopper, or even new characters introduced in that episode could be important.
I should include the voice actors and translators involved. Horriblesubs usually has a list of contributors on their site. Mentioning the voice actors like Brian Neubert for Luffy could be useful. Also, the translators and encoders who work on the dubs.
Lastly, community reactions and reviews. If there are any forums or sites where fans discuss the episode, that could be helpful to mention.
I should also mention the differences between the dubbed version by Horriblesubs and the original Japanese version. Are there any notable changes in translation or voice acting that fans should be aware of? For example, sometimes groups take creative liberties with translations.
Next, the user probably wants information on where to watch it. Since Horriblesubs is a group, they might release it on anime platforms like Crunchyroll, but sometimes they have their own methods like torrents or direct links. However, I should be cautious about linking to unauthorized sources. The user might need guidance on how to legally access the episode.