Among Serbo-Croatian (SC) clitics, the interrogative li seems to be unique in showing a peculiar type of sensitivity with respect to the type of host it cliticizes (on)to. Whereas li is unproblematically hosted by a finite verb, when hosted by an l-participle, the outputs are treated as fully ungrammatical. Be it in syntax or in phonology, current accounts in the literature overgenerate by predicting the ungrammatical constructions to be grammatical, and undergenerate by predicting grammatical outputs in SC to be ungrammatical. Moreover, native speakers’ judgements regarding the l-participle li construction suggest a more gradient judgment than standardly assumed in the literature. We present results of a large-scale experiment undertaken not only because of the unclarities regarding the acceptability judgments we encountered for l-participle li, but, first and foremost, because of the lack of prior empirical investigations or established baseline of acceptability in the domain that has, otherwise, been a prolific and important domain for theorizing in SC. On the theoretical side, we argue that the crux of the solution is not due to the defectiveness of li (as previously argued), but due to the [-finite] nature of participles. Testing our hypothesis against the data obtained in a systematic manner, we further demonstrate that the gradedness in (un)grammaticality judgments are accounted for by analyzing the interplay as well as the tensions that arise at the syntax-phonology interface.