depending on what client is used. normally, DHT can't ruin anyone's ratio at all, yet it's totally useless for private trackers in general, since it only provides nothing else but list of peers. uTorrent, for instance, needs the exact torrent-file hashes so that it can take some avail from DHT. as long as every user has his own passkey which is "stamped" into his torrents, these torrents differ from other torrents, hence DHT can't "find" them.
much more dangerous {and possibly harmful} is the function of "sharing torrents" implemented in some clients. this is also useful only, if both sides use the same client. however, it may reveal your passkey.
as for this tracker, i think, i already "discovered" the "security hole" alleged by some users. in fact it's no "security hole" but the users' mistake, because of misunderstanding some tracker facilities. if you aren't sure what some of them are about, better safe than sorry and post your querry. i can't unveil the details in public, since many greedy downloaders might misuse this information for their purpose at the expense of the unaware users.