1.) For starters:
http://forums.spiralknights.com/en/node/35902
2.) I have never done Roarmulus Twins on Kitty-Softpaws. As well as majority of these achievements. These are actually my main's achievements. Or are they suppose to stack up together.......?
http://i1221.photobucket.com/albums/dd475/HectorUribe/spiral_2011-12-10_...
Same account, shares the achievements. WoW does achievements per character.
I see no problem with multiple characters, or "save files". You do know this is how 99.9% of video games work, right?
Well, Xylka-Mkii, usually the games have more privacy in their documents and also have different types of files saved per file. A folder corresponding to it etc. Or in my case, different content for different characters.
Do you use steam? if so, it'd be weird to have double or triple achievments.