I need to look back to be sure but I think pidgin appends these characters for some pidgin specific reason. I thought I was removing them so they either changed them or I missed those. I will take look at it this weekend.
I got this too and I think I figured it out. There are two things I did that stopped it from happening. The first one is unlikely since its applications specific, but I forgot the command and am having trouble finding it. It had something to do with stripping html from the sms, but since it dealt more with irc chats than gvmax, that shouldn't be it. Say if the next thing doesn't work. The second thing I did was turn off OTR (off the record). For me on bitlbee on irssi (linux) it was "set otr_policy never" but it'll probably be different for your client. One of these two options stopped the tailing characters.
btw, it seems /u0009 is the ASCII or something for the tab space. I think gvmax or our clients might be adding a tab after our messages which then translates to /u0009. pure speculation on my part though.
The 0009 characters are added by some gtalk client can't remember right now which one. It is used by the client for some client specific function. When I get back online I'll look that up since I have code to deal with these (although I guess something changed)