Originally Posted by BCRider

The issue isn't when they are used inline like they were intended for doing. It's when we use them as final levers and have to terminate the thimble somewhere that isn't normally used for such things. Like you've done by using interrupter levers as end levers instead of inline.

The original issue arose, IIRC, when the other guy used them as primary levers on mountain bike style bars. He wanted nice tidy and small two finger levers. So he used them the right way around instead of backwards like you're doing. But he then set himself up to run into problems when he simply ran the road style end thimbles into the movable lever portion.

On normal levers the thimble sits into a pivoting block so it can turn. So it keeps the thimble in line with the cable pull. But interrupter levers don't have that pivot. So every time he pulled on the levers the cable was being pulled into a sharp kink right at the thimble. And after a couple of months he broke one cable and noticed fraying on the other.

Part of his issue was also that he kept his levers set up fairly loose. So the cable had to move a lot. But in the end it was really the lack of a pivot or any way of moving the thimble out to where it can be stable.

Your levers don't have any pivot. But you've put the thimbles into the adjuster barrels. So the cable right where it comes out of the thimble is not going to see any bending. And that's the good thing. So you should be OK. But I'd keep a close eye on the cables where they flex in the lever for some time just to be sure.