International and regional human rights treaty mechanisms have acted as de facto avenues for implementing international humanitarian law (IHL), including through decisions on reparation. In light of the scarcity of other options for victims, human rights bodies will remain relevant actors in this domain, despite criticisms related to their alleged fragmentation of IHL’s universality; perceived partiality owing to inability to address non-State actor accountability; and potentially selective, individualised approaches to reparation for mass violations which may clash with collective processes. This article examines the case law and practice of the main human rights treaty mechanisms in light of these criticisms to determine how far they may still be warranted, particularly in the field of reparation. It further aims to identify precedents indicating potential ways to address remaining issues. It finds that practices have been developed which show the possibility of mitigating concerns in all three areas. Regarding fragmentation of IHL, the risk in any event appears low; on the other hand, the mechanisms’ capacity to address the non-State actor issue are structurally limited, requiring action on other levels. Finally, regarding the interplay of individualised international claims and collective domestic processes, there is room for further empirical observation regarding effective strategies for international or regional mechanisms to address both individual and societal interests in reparation.