Hydrino theory is already 33 years old - and this is first time it's emerged in mainstream journal publication, I guess. The existence of hydrino looks controversial even for me, who collects various anomalies and controversial topics. Before some time I started to speculate that phenomena which Randell Mills attributes to cold fusion are actually overunity effects analogous to cavitation heaters and magnetic motors. This aspect various observations (like the overunity of Langmuir atom hydrogen discharge and let say Chernetski and Papp's plasma generators) would have common with Randell Mills process. From both quantum mechanics, both dense aether model follows, that subquantum energy levels of hydrogen should be indeed possible, but they would require pumping of energy into it, i.e. hydrino - even if it could somehow exists - would be metastable. And its formation wouldn't definitely serve as a mean of energy production, neither as an explanation of dark matter and another phenomena, which Randell Mills routinely attributes to hydrino.
The principal reason here is the omnipresent vacuum noise (so-called Zero Point Energy or ZPE) which leads into degeneracy pressure, i.e. the fact that vacuum behaves like water surface filled by Brownian noise, which wiggles with small particles and objects and takes them apart. This wiggling is for example the reason, why liquid helium doesn't freeze even at zero Kelvin temperature, i.e Zero Point. The finite diameter and fundamental quantum state of hydrogen atoms (and another atoms indeed) is thus result of equilibrium between degeneracy pressure and attractive Coulomb force. The same quantum noise would also prohibit the collapse of matter into singularities predicted by general relativity - so I believe that black holes behave merely like very dense stars with physical surface blurred with space-time up to higher or lower degree, which mostly depends on the speed of their rotation.
Unfortunately the situation is not so simple and more detailed analysis will be still required. From dense aether model also follows that concentration of energy at some place makes vacuum more dense like soap foam shaken inside closed vessel. The increased vacuum density slows down the propagation of energy (it's common mechanism for both relativistic phenomena like gravitational lensing, both quantum mechanic phenomena, like pilot wave and probability function). In addition, increased vacuum density makes forces (including Coulomb force) weaker, because it essentially works like space-time dilatation (and distance increasing) for them. The situation gets even more complicated at the proximity of surfaces of normal matter, preferably within narrow cracks and cavities of metals, which would stabilize these subquantum levels even more, because the surface of refracting bodies also shield portion of ZPE noise.
So that maybe - just maybe - some of sub quantum states could be actually more stable, thus allowing some subquantum atoms and/or even their compounds actually exist. Other than that the spectral lines attributed to hydrino in Randell Mills experiments could be also manifestation of Auger transitions, so that definite proof of hydrino is waiting for its publication.