According to the most recent version of Relativized Minimality, the ungrammaticality of weak islands is the result of featural similarity between elements in an intervention configuration. The theory posits that only features triggering movement have the potential to induce intervention effects leading to ungrammaticality. However, recent advancements in the theory have extended the set of features claimed to generate intervention effects to encompass lexical restriction. This theoretical move encounters several empirical challenges. In this paper, we address this question in 3 acceptability judgment experiments in French. We explore how featural similarity influences acceptability judgments across both wh-islands and minimally different grammatical structures, that-clauses extraction, focusing on three distinct features: (i) the feature associated with question operators, (ii) lexical restriction, both anticipated to show intervention effects according to the most recent version of Relativized Minimality, and (iii) animacy, which is not expected to show such effects. Results indicate that featural similarity in lexical restriction and animacy exerts a mild influence on acceptability ratings in both islands and grammatical structures, contrary to what predicted by Relativized Minimality, while similarity in the feature associated with question operators exerts a strong influence. We propose an empirically motivated account that restricts the set of features relevant to grammar-based effects à la Relativized Minimality to core syntactic features triggering movement, and groups together the milder effects arising from similarity in other linguistic features, like lexical restriction and animacy, as resulting from similarity-based interference in memory.