Have a look at https://en.wiktionary.org/wiki/User:Yair_rand/addcomment.js
It allows you to add a comment, signed and correctly indented, to the end of a section of a talk page.
It works fine on my Android phone, which is more than can be said of the regular edit function.
The discussion (ironically in Liquid Threads) is found here, https://en.wiktionary.org/wiki/Thread:User_talk:Yair_rand/Comment_gadget