Sometimes this works, sometimes this doesn't. However, I started a new character under 1.0.11 and took viking magic. I cast Magic Steel twice, once on accident. My mana started diving quickly and I couldn't figure out why until I tried to cancel magic steel and realized I had two copies running.
The flag seemed broken in at least half the RC versions. I guess the final has this problem too. That makes my cat cry. (Not really, he cries all the time anyway. I think it is allergies and/or idiocy.)
Playing a new Character with 1.0.11 + DLC and no mods. I can stack the Astrology Buff "Radiant Aura" up to two times on my character.
Yes, I'm experiencing the same bug with Radiant Aura. One of the ways you can get these buffs to stack (or at least Radiant Aura) is to change floors after casting the first buff. Reloading the game (so the buff partially falls off) may also allow the stacking (haven't tested those yet). edit: This stacking seems to be able to go on forever. I've now stacked my Radiant Aura 6 times, giving me a Visual Sight Radius of 12, and 6 Righteous Damage, 6 Necromantic Resistance, 32 Enemy Dodge Reduction, etc. It's ridiculous. edit 2: Ok, getting damaged or having the buff partially fall off isn't letting me recast it.
Here, I got a screenshot of my Radiant Aura with 20 stacks. This is very exploitable, as long as you're willing to change floors whenever you have enough mana to cast it again: As you can see, I have over 100 Enemy Dodge Reduction and Magic Resistance.
lesser syzygy is stacking still too. I was running around with 4 of them last night. Of course I could see now how many stacks I had. But with mana maille it seems like serious bug.
Yeah its pretty funny. If you've got 20 of them running at a time you drop mana really fast, you can go really negative, and then it resets back to 0 during your next turn. Its actually kinda funny to watch. Does totally screw up your mana curve though.