I've tried Sublime text as well, and I can change "spider" to "blob" - it just doesn't work (cannot load malformed bytecode).
I also tried changing the preceding \x0b to \x09 (it seems to be length + 5) but that didn't make it any more valid.
I tried changing spider to blob\0\0 to keep the length, but that was too optimistic.
I.e., there might be some other places in the bytecode that doesn't work if the string changes length, so as others have reported, I can only change strings to something of the same length.
Edit: I figured it out - it was too simple You can use the LUA source code from the first page directly in as a replacement for the bytecode, instead of editing the byte-code. The source can be edited with a normal text editor.
Now I just need a source file for levels containing spiders.