In the composite you have the 7th ruler mars strong in its own house and conjunct its own cusp, so the relationship will have a martian quality to it, exasperated by being combust with the sun, ruler of the 4th.
Venus is also strong by sign, but not connecting with the energy in the chart, and in a love or romantic relationship you would want Venus to relate, so this is a weak spot. It does have a semi-sextile with Chiron but this would not be expressing affection, but healing one of the partners at the expense of the other.
Uranus on the midheaven of social status symbolises the unusual and original nature of the relationship, and south moon's node here could indicate that their reputation suffers for this. Moon is inconjunct this position, creating nervous tension as a result. This could relate to the one partner not coming out publicly.
Saturn on the ascendent on the other hand, shows a traditional, serious face put on for the world.
Probably the most significant aspect here is that Moon squares pluto on the cusp of the 8th of sex, so there is a current of deep feelings and intimacy between the two, but also jealousy and possessiveness created by the fear of losing each other. This can easily turn into manipulation and obsession. There is a sense of exclusiveness, and over time it undermines the relationship by creating a fear of rejection or of a change in their situation.
With pluto by the 8th house these scenes will be played out not only on the sexual level, but on a deep lying subconscious one, stirring up psychological demons that are hard to handle.
There is a tendency to try to control the other on an emotional level, with one partner continually digging into the inner feelings of the other creating an explosive atmosphere, that can eventually lead to a dramatic breaking off. it starts off well and intensely but the energy becomes just too controlling and manipulative.
This may be what the reddit writer was referring to, not sure, you should really ask them.
With Venus unrelated, and the moon in this stressful position, it would be quite difficult to overcome the tensions and have a long range relationship between the two persons.
