You messed up a DSi with DS brick code? I have never heard of that before and it should not really be possible -- the DS lite largely fixed the bugs in question (as did flashme on the original DS) and that would be a regression in security.
There could be a new bug that was exploited over the ones used by DS malware and there could well have been a regression but I have tried to follow this area (homebrew/hacking delivered brickings and corruption of devices), especially for the DS family and had not heard anything like that. Equally I have to wonder if there was not some kind of short or something on the pins, such a thing has killed many a device over the years.
Basically in the security world there is a term called "movie plot threat", this is not quite that (it is quite realistic to be able to make DS bricking code if you really cared, unlike being able to blow things up by hacking, and any marginally competent ROM hacker that has got as far as basic assembly hacking could do things here) but every time this has come up it has been people worrying about nothing for no reason. I guess this is what tbb043 and I wanted to head off the pass as it were.
http://www.darkfader.net/ds/ has more on the two out there that you are probably referencing. I believe some copied it into ROMs/padded it out into ROM size and maybe changed the icons, I am not aware of any doing anything I would call proper hacking for it (I am half reluctant to say as saying is 90% of the way to a guide and I would really not inspire idiots that can not take the 5 minutes to figure it out otherwise).
As far as I am aware there was never a version with fake flashme. It was proposed in a discussion once (if flashme protects you then if you get people to bypass it thinking it is an update to flashme...) but I never even saw it worked up into something like that.