In my (rather limited) experience with Librans (I'm Gemini) we have a nice banter, that goes between light chatting to more deep chatting. I believe it's rare that we have nothing to say to one another.
As in if the Gemini became too similar to the Libran? I have certainly found myself moulding a bit to my Libran friends. My main Libran friend prefers it when we disagree, rather than agree - eg on a book or movie or whatever.
I think these two won't melt into each other. Just as Aquarius and Libra won't melt into each other. We're ruled by different signs. Venus and Mercury are markedly different, and their way of presenting themselves are as well.
The way they connect is through the intellect. (Venus yields, of course) They have an instant rapport with each other. However, gemini is more mentally ambidextrous in the sense that they juggle many topics in the same conversation, sometimes to purposely divert the course and confuse the scales.
I don't post as much but I do read most everything.
I can tell you how my (Gemini) and my guy (Libra) interact. We both seem to "get" each other. We laugh and joke a lot and always seem to be on the same wavelength. We have known each other more than 25 years. We've been in and out of each other's lives throughout that time (currently in again), but we always seem to connect when we start thinking of each other. We never have dull conversations. We tease and talk lightly about things, but we've also discussed some deeper emotional things. The sexual tension between us is huge and we play off that. I like his calm, seductive sort of personality. He says he likes my energy and playfulness. On the negative side, there are times when I know he's "processing" things and I can't tell what he is really thinking. And it bugs me when he pulls back and then returns like nothing changed. But on the other hand, I know I pull back sometimes as well because I just get into something else for a while and it doesn't seem like a big deal to not be in contact with him for a few days.
I have always seemed to be attracted to and click with Libras. Hours go by like minutes when we're together; it's never dull.
I've never met a Gemini male or Libra female (that I know of), so I don't know how things differ between the sexes.