Marc,
I agree it's nice that all readable european, asian, etc. characters come out unescaped, but it's weird to know that Gambit would come not-copy-paste-proof out of the box, and that you need a specialized script at startup to fix that.
I use the best terminal software and it does not show all unicode characters;
To understand the implications of unescaped Unicode characters, I read up on
http://unicode.org/charts/ and other places, and it seems that the worst abuse of Unicode characters is illustrated here
http://www.marlborotech.com/Zalgo.html , and maybe also the right-to-left/left-to-right characters can cause disorder - it's quite bad but not fatal.
I would primarily suggest that a command line option would be added that configures the escaping e.g. -:E , -:E127 (or maybe -:T127 for terminal and -:F127 for files).
Secondarily I would suggest reverting lib/_io.scm:13119 back to (##integer->char 127) i.e. escape all >127 again, as at least I find this to be really more a "safe by default" behavior.
Anyone else has any thoughts on this topic?