I don't think you have to care about what your neighbors say...What you do in your own house/basement and what type of window blinds you use should only concern you, not them. I don't think a curtain draws up attentionor seems suspicious but just for the sake of your peace of mind I went online and found a type of window covering thatseems suitable even in a basement and provides the level of intimacyyou want:
Availablein four different slat widths (25mm, 35mm, 50mm and 63mm) thisnatural product provides a warm and contemporary look to any room.Like its sister product the Venetian, a made to measure wooden blindis also extremely versatile and allows excellent light control aswell as complete privacy. We have a wood colour to match anyfurniture and also now available in the ultra modern and funky glossblack and white. Direct Blinds also now offer the new and innovativeprivacy range exclusively to you, not readily available online.
I hope my advice helps, butfor future reference Iwouldn't recommend coming up with fake stories about what you do withyour life or in your basement. Keep it simple!