Is It Normal to Feel the Valve of Breast Implants?

Yes, it is true. In thin patients, particularly with larger implants,  the breast implant valve can be palpable

I am going to assume that you had extremely thin tissue (ie little to no breast tissue) before your augmentation and that you had the implants placed above the muscle.  So if the implants are above the muscle then they need to be placed beneath the muscle to provide an extra layer over the implant .

Dr. ES

It is farily normal to feel the valve of a saline implant underneth the nipple areola complex. This is especially common in thin women.

The modern saline implant valve complex is rather flat and non-projecting and located at the topmost portion of the implant. As a result, they are very rarely felt and only in some women with almost no breast tissue in whom the implants were placed over the muscle.
A better option in such patients are silicone gel implants which are lighter, ripple less and which have no valves.

Dr. Aldea

It is not unusual for a saline implant placed above the muscle in a thin woman to have a palpable implant valve.  If this is your situation, your options include moving the implant to a submuscular location and changing to a silicone implant which has no valve.