Yeah, I did state that it was pretty obvious in ESB, but not in ANH, that Palpatine was a darksider, and it probably wasn't until ESB that they decided to have him be a darksider and have a part in Vader's downfall, as well as a bigger threat than Vader, apart from the puppet ruler from the novel.
However the Sith/Darth stuff wasn't really a big thing until the prequels, although previous Dark Horse comics did feature Dark Lords of the Sith, and a 1996 comic also had Emperor visiting the Sith home world of Korriban (Now canonically 'Moriband") but movie-wise he wasn't really a Sith until the prequels I think. Although Lucas's version of the Sith-now pretty much the 'canon' version-was different from how the comics envisioned them, meaning that there were a lot of retcons along the way until Disney just started from scratch.
I think the main hint that Palpatine and Sidious were the same person, apart from their similar voices and lower faces, as well as a fairly obvious number of plot points, is that the balcony that Palpatine talks to Maul on is visible outside Palpatine's TPM apartment when he later talks to Amidalia.
However the Sith/Darth stuff wasn't really a big thing until the prequels, although previous Dark Horse comics did feature Dark Lords of the Sith, and a 1996 comic also had Emperor visiting the Sith home world of Korriban (Now canonically 'Moriband") but movie-wise he wasn't really a Sith until the prequels I think. Although Lucas's version of the Sith-now pretty much the 'canon' version-was different from how the comics envisioned them, meaning that there were a lot of retcons along the way until Disney just started from scratch.
I think the main hint that Palpatine and Sidious were the same person, apart from their similar voices and lower faces, as well as a fairly obvious number of plot points, is that the balcony that Palpatine talks to Maul on is visible outside Palpatine's TPM apartment when he later talks to Amidalia.