My feet are right at the top of most size ranges, which means I am constantly wearing holes in the toes. I have taken to darning the hole - or often sewing over the thinning patch to reinforce it before a hole wears through.
Whenever I see instructions for how to darn they use straight stiches like shown in this article, but I don't feel that having a solid patch in a stretchy fabric works well, so use a netting style stitch instead so it has more give. (when I get some time I might do some pics/a tutorial to show you).
Does anyone else darn their socks (or any other knitwear) and if so what type of stitch do you use?
Thin fabric is not a problem - people used to repair stockings with ladder darners. But they are best used if single threads snap, creating a ladder. If the fabric is overall weakened, it's probably not worth working with a ladder darner (a fidely business), since the original thread is unlikely to hold on it's own.