Parler, a "free speech" platform popular with conservatives, was taken offline in January 2021 due to the lack of moderation of hateful and QAnon- and other conspiracy-related content that allegedly made it instrumental in the organisation of the storming of the US Capitol on January 6. However, Parler co-existed with other social media platforms, and comparative studies are needed to draw conclusions about the prevalence of anti-social language, hate speech, or conspiracy theory content on the platform. We address this through a cross-platform comparison of posts related to QAnon. We compare posts with the hashtag #QAnon on Parler over a month-long period with posts on Twitter and Gab. In our analysis, Parler emerges as the platform with the highest average toxicity of the posts, though this largely stems from the distinctive way hashtags are used on this platform. Gab has the highest proportion of #QAnon posts with hate terms, and Parler and Twitter are similar in this respect. On all three platforms, posts mentioning female political figures, Democrats, or Donald Trump have more anti-social language than posts mentioning male politicians, Republicans, or Joe Biden. An analysis of entities mentioned in posts revealed differences in content - with Twitter posts mentioning prominent figures related to QAnon, while Parler and Gab posts mention entities related to conspiracies. Narrative analysis indicates that the discussion on Twitter centres on QAnon and is critical of it, Parler focuses on supporting Donald Trump, while on Gab the discussion focuses on more conspiratorial content, in relation to both Trump and other political figures.