Upvote:1
Does Buddhism consider neutral habits, just habit itself, as unvirtuous?
Nothing is a habit in itself. They consists/occurs out of something else, and can be viewed as sankhara.
Is doing something repeatedly without reward, compulsively, a kind of potential attachment?
Yes, there is silabbatupadana - clinging to rituals - for instance. However, one may benefit from specifying what is meant by habit. Sometimes we persevere because we're hard wired that way, and it could arguably be a case of rupa, our constitution.
Upvote:3
Kilesa has a residual impression which is called vΔsanΔ which even arhats (other than the Buddha) have. Only a Buddha eliminates that. This is what drives habits. Many habits are reflexive and there no much thoughts of the intention behind it. If it is purely reflexive it does not have karmic consequences.
Initially, when you start doing something this is driven by craving. More you do it it becomes habitual. When it becomes habitual this might surface without craving.
If you think you are developing bad habits you should break them early. Deeply ingrained habits are difficult to break.