That's an interesting question, Sean,

In fact, where the 'seul' is placed can change the meaning of the sentence.

If you say -

'et c'est ainsi que notre bûcheron ne se sentit jamais plus seul', meaning he never felt more lonely 

et c'est ainsi que notre bûcheron ne se sentit plus jamais seul = and that's how our lumberjack never felt lonely ever again

and using 'plus jamais' avoids the confusion, so I agree with Aurélie here!