Congrats on the knots. That still doesn't change the fact that they can break when you kink them and they are more fragile than a descent RCA cable. I know, I have ruined an optical cable by accidentally kinking it. I have yet to ruin an RCA cable's cable part. Now, I have had issues with RCA cable end connectors, but I've also had issues with TOSLink cable end connectors too.
As for connecting them, as long as you get a good connector that keeps the ends properly aligned, it shouldn't be an issue. I connect 2 12ft cables together for a 24ft run, which works great.
If you paid me to break a Toslink cable, I'm sure I could do it. That is not the same as "fragile."
In 20 years or so of using Toslink cables, I have never damaged one. OTOH, I have 3 cats who have been able to gnaw through a number of coax cables during that time. But I won't say they are fragile, either.
If the only drawback that can be cited for Toslink cables is that they are "fragile" then I suggest someone is really, really reaching for one.
I have some fairly high end HT electronics. My A/V Receiver, a top of the line Denon, has 8 user definable Toslink inputs, and only one digital coax input. Many lower end don't even have a single digital coax input.
So at both ends of the market, Toslink has at least an 8 to 1 acceptance factor over coax. Seems like the market has spoken.