Your comments

Although it is a little different from title , I want to jump definition or use of function, or variable in another file such as Vim or Emacs do with ctags.

I think it is too heavy for iPad to make lists of function and variable in some situations.
So, preparing data(ex: ctags, csv, .sqlite) as list is better than Textastic make it.
Thank you for fast reply.

I read link of your comment.
As you wrote, it seems like problem of marked text.
 Maybe it is not need to tell which keyboard I use. But just to make sure, it occurs with both Bluetooth and screen keyboard.