This is not a complaint, but I've got a number of nodes in the -5 to -10 range now, and wondered if that was typical.

Typical for what? Asking questions about stuff that's already covered in numerous other locations? Yes, I guess that is typical for that situation. Typical for a new member of Perl Monks? Probably not -- most new members lurk for a while to get the 'feel' of the place before posting.

How low can they get before possibly being removed?

Nodes don't get deleted as got lower into the nether regions of XP -- they just climb the list of the worst nodes.

Can anyone offer me any advice to avoid being so apparently bothersome to others?

Learn how to use the Internet to find what you are looking for. If you put an honest effort into searching and still come up empty, boil your question down to the barest essentials and post that.

Meta discussions about XP and whatnot are a tiresome. An earlier reply to your original post suggested you compare your best nodes to your worst nodes: that's a good place to start. See if you can infer what makes a good node, and just as important, what makes a bad node. You may come up with the following:

I hope this post was useful to you. I wish you well on your journey.