Your result is definitely negative for HSV-1, and almost certainly you don't have HSV-2 either. As you apparently know, HSV-2 results 0.9 - 1.1 are technically equivocal, meaning no conclusion can be drawn. However, since the manufacturer developed that recommendation and secured regulatory approval to interpret the results that way, extensive research has shown that almost no results below about 1.5 are truly positive. No medicine is known to alter the test results; clindamycin certainly does not do so. The biological reasons for equivocal results are not known.
If it were me, knowing what I know, I would just interpret the result as negative, especially if I had no symptoms of genital herpes or other reason to be highly suspicious I was infected. But if you want to pursue it further, the first step should be to repeat the same test; most likely the result will be clearly negative (below 0.9) and the issue will be resolved. If a repeat test continues in the borderline range, you could then have either a BiokitUSA HSV-2 test, or a Western blot test (expensive).
For more information about all this, take a look at this thread from a couple of months ago:
http://www.medhelp.org/posts/show/593272.
I hope this helps. Best wishes-- HHH, MD