This subject might always generate some controversy.
The full legal name of British knights takes the form "Sir John Doe, Knight". (or Knight Bachelor).
If you look at the primary sources throughout the middle ages, you'll see that knights are always named in this way in formal documents. It is still the correct legal form of their names.
In the early middle ages, Sir was used for both priests and knights. Before about 1200 Sir often takes the form Sire or Monsire. (This is part of the transition from using French at the English court to using English.) After about 1200 Sir begins to be restricted to knights. There was an intermediate period where Sir seems to have been used indiscriminately as an honorific for anyone who did not have a more specific title. After 1611 Sir has also been used for baronets.
Strictly speaking, you would use "Sir John Doe, Knight" (or Kt. or Kt.B.) to make a distinction from "Sir John Doe, KG" (a knight who belongs to an order) or "Sir John Doe, Baronet"
However, our modern tendency is toward relaxed usage. Sir is so universally established in the public mind as meaning a knight or baronet that many people think adding Knight is redundant. As a result, many modern encyclopedic standards use Sir for knights, and specify the details only for knights of orders (KG, KT, etc.) and for baronets.
It is not correct to drop Sir for baronets, any more or less than for the others -- all of them can appear with only a suffix, and all them can appear with Sir.
So, as we work toward refining the Geni standard we are debating whether to use the full legal name and style, or to use a conveniently abbreviated modern form. As we continue, let's keep in mind that there will be users with strong opinions on both sides.
http://www.geni.com/projects/Naming-Conventions-for-Knights/11429