I don't remember having any problem with case sensitivity. The only spelling-related issues I can think of that caused me debugging problems were in languages like Bash and PHP and they were, most of the time, typos, not bad use of upper/lowercase. I see your point about case-insensitiveness being more human-friendly but I think that these problems are caused either by not using the right tools or not having a clear style policy. Also, call me a fetishits, but my eyes bleed when I work with code with inconsistent style conventions. I can't stand code which uses a different convention for each line and, of course, things like 'KEanu_reVeS' and then 'keaNureves' will make my head implode.