I don't know if you are still interested in feedback on this, but your question caught my eye, because I have been wondering about the same. The case hasn't really been mentioned that much where I have looked, and the same aspect exists in the horoscopes of me and boyfriend:
Venus is the ruler of both my ascendant in Libra, and my sun sign, which is Taurus. It is placed in Gemini at 28.38 degrees. So of course this planet is really important in my horoscope.
My boyfriend has Mercury as ruler of his ascendant in Virgo, and also as ruler of his sun sign Gemini, and it is placed at 23.11 degrees Gemini. So the "double effect" of the ruler is also present in his horoscope.
His sun in Gemini is placed at 4.34 degrees, and conjunct with my Mercury at 6.51 degrees.
Concerning the chart ruler interaspects, I read something interesting in Stephen Arroyo's book Astrology, Karma & Transformation on page 247-8 in my edition. I have to translate it from danish, since that is the version I have
"A synastry factor which should be offered special attention to is the situation where to persons chart rulers (rulers of their ascendants) are related in an aspect. The exact aspect type is not that important, as the fact that there is a relation between two individually dominant orientations of life. (I have left some of the text out here) I always interpret an aspect between chart rulers as a sign of the fact, that these two persons most likely will have a relationship of extraordinary strenght and importance. They often have an extremely strong karmic bond between them, and the fact that such synastry factors are much rarer than the case where the one persons ascendant og descendant are placed in the same signs as the others birth planets, should make us pay special attention to the cases
There is a bit more after this, but maybe you can find the text, the whole book is really interesting.
An aspect between chart rulers must be really important in my opinion, even though the fact isn't emphasized in any other book I have read.
The aspect between my ruler and my boyfriends is a bit wide, but the fact that they are placed in the same sign must be relevant as well. Maybe especially since the two planets are "double rulers" in both our horoscopes. I think the influence of the aspect is quite significant in our relationship, but I can't really be sure because of the conjunction between my Mercury and his sun in Gemini. I often feel "warmed" by his way of being, but I guess that is his sun warming my heavily aspected Mercury. But humour and communication is really important, and I feel that we understand each others way of thinking intuitively (in most cases
), and that could very well be caused by the mercury-venus aspect.
I hope that this input is useful to you, and that you still are enjoying your relationship,