If you have been using mIRC for many years and you have only seen it corrupt the ini file on so few occasions during that time, and it is one of your most used applications, that seems to imply that it is pretty reliable. At such a low rate of incidence, statistically those few occasions where the files were lost could be attributable to almost anything eg. Windows issues, background applications, anti-virus/security software, and so on.
mIRC opens, writes, closes, and flushes all files to disk immediately.
mIRC saves files in a two step process. It creates a temporary file first, saves all settings to it, and only if that is successful, with no errors, does it then delete mirc.ini and rename the temporary file to mirc.ini. If there is an error of any kind during the process, it leaves the original mirc.ini untouched. This is the safest way to update files.
In this case, both the mirc.ini and servers.ini were corrupted which implies that something else has happened. When Windows is in a low resource state and Windows and/or applications are unable to allocate memory or save files to disk, and end up freezing/crashing because of the low resource state, almost anything can happen unfortunately.
That said, as I have never been able to reproduce this myself, if someone can find a set of steps that reproduce this reliably while forcing a Windows BSOD (note that this really could result in file corruption in Windows or other applications), I will try to follow your set of steps to reproduce it.