I've been suffering a really annoying bug in VIM recently: when repeating an action that introduced space characters to the buffer (that is, single-byte 0x20 ASCII-compatible space characters), the action would insert Unicode non-breaking space characters instead (0xc2ac).
I've finally tracked this down to an old
vimspell plugin. Version 1.100 /
released 14-Sep-2005 causes this in conjunction with the Debian
package, version 2:7.2.245-2 (and perhaps others). The solution for me is to
just remove the
vimspell plugin: the upstream author recommends that users
of VIM versions 7 and upwards use the built-in spell checker instead anyway.