Please note: I considered posting this as an answer to the initial thread, but I feel that this question warrants its own, targeted answer set. There's also a follow-up tag, so I figure I'm above the board.
I'll tell you straight-out what I hate about line numbers: they poison my clipboard. Many sites have numbered code blocks that translate to my clipboard. I can't STAND when that happens! What's worse, webmasters who have users stripping numbers from code simply can't be told.
On the other hand, I also think find it very frustrating that stackoverflow, being a programming Hall-of-Famer and all, hasn't implemented a simple yet eloquent code referencing system. We can accommodate concerns like the one I've mentioned above, and I trust users to follow the FAQs and tool tips, and not post lengthy code blocks.
What problem does having numbered code blocks solve, and why is it worth the effort to implement? I like to keep my tabs and programs down on my clunky old POS PC. It's irritating to have to open something new up and clear my clipboard. The only other option is to alter local style sheets or count--1, 2, ..., 25, ..., I lost my place, 1...--just to get a line number!?!! WHAT?!
Hey..., wouldn't it be cool to have deep embedding at StackOverflow, so that users could link directly to relevant lines in code blocks? Save us all some time.... But before I get histrionic, how about we get together around an old standard (see the link):
What is your opinion?
Would you rather have an low-resource function allowing users to toggle line numbers attached to code blocks or would you rather not? Please, explain your choice so that we can all think on and respond to some solid reasoning.
Thank you in advance, for your creative and unique responses!