This is too open ended - there is no standard for this kind of information, either a coder will have his own style, or there may be a company style. However, have a look at this: http://www.icsharpcode.net/technotes/commenting20020413.pdf
] - it's on commenting generally and covers modification history.
BTW: Modification history should be a part of the XML comments you attach to your methods - or rather don't in the example you give. See here: http://msdn.microsoft.com/en-us/library/ms172652(v=vs.80).aspx
]. It can make a big difference to use them as Intellisense can pick them up if nothing else!