  The first detection of gravitational waves from a merging double neutron star
(DNS) binary implies a much higher rate of DNS coalescences in the local
Universe than typically estimated on theoretical grounds. The recent study by
Chruslinska et al.(2018) shows that apart from being particularly sensitive to
the common envelope treatment, DNS merger rates appear rather robust against
variations of several factors probed in their study (e.g. conservativeness of
the mass transfer, angular momentum loss, and natal kicks), unless extreme
assumptions are made. Confrontation with the improving observational limits may
allow to rule out some of the extreme models. To correctly compare model
predictions with observational limits one has to account for the other factors
that affect the rates. One of those factors relates to the assumed history of
star formation and chemical evolution of the Universe and its impact on the
final results needs to be better constrained.
