Can bad honing technique spoil a knife?
Poor honing on a blade that was already in true can reduce the sharpness, as you have discovered.  This happens if your angle is off, and you knock the edge of the microscopic burrs or teeth over, presenting a duller cutting surface.  

It is likely that proper honing will correct this, although it may never be quite as perfect as the blade fresh from the whetstone or factory.

In any case, you will not do any permanent harm to your blade with a honing steel (short of using it as a bludgeon), because absolute worst case, you can always have your knife resharpened, or do it yourself.   This may be somewhat inconvenient or costly, but is much less expensive than replacing a blade.