This usage is explained in CoGEL (A Comprehensive Grammar of the English Language).
(CoGEL § 6.27 Optional reflexive pronoun The basic reflexive pronoun is sometimes optional, in the sense that it may acceptably be replaced by the more usual ordinary objective pronoun. The self-forms are chosen to supply special emphasis :
(a) […]
(b) In 'semi-emphatic' use. Here the reflexive pronoun normally receives nuclear stress. It does not have the subject as its antecedent, but is commonly used as a more emphatic equivalent of the 1st and 2nd person personal pronouns. Especially, however, when it replaces I and me, myself is felt by many to be a hyperurbanism, a genteel evasion of the normal personal pronoun. The reflexive pronoun in these contexts can be reasonably called 'semi-emphatic' because it can be regarded as an abbreviated version of a sequence of the personal pronoun followed by the emphatic reflexive pronoun (you yourself, him himself, etc). Thus there are three possibilities in:
- Anyone but {YOU/yourSELF/you yourSELF} would have noticed the change.
The latter repetition of the pronoun (you yourself) is avoided, however, outside the subject position. The constructions in which the 'semi-emphatic' reflexive occurs are the following :
(i) […]
(ii) When a reflexive pronoun (particularly a 1st person pronoun) is coordinated with another phrase:
- They have never invited Margaret and me/myself to dinner.
- This is a great tribute to the Scout Movement, and to you/yourself as its leader.
In this construction, the reflexive pronoun is not limited to 'object territory'; it can replace a subjective pronoun:
- My sister and I/myself went sailing yesterday.