I was somewhat surprised when reviewing the Full Paper Template from the Journal of Computational Chemistry, which states that the abstract text should contain "no personal pronouns". I have seen many articles which go against this and even several that have been published in this journal recently (http://onlinelibrary.wiley.com/doi/10.1002/jcc.24217/full, http://onlinelibrary.wiley.com/doi/10.1002/jcc.24225/full, http://onlinelibrary.wiley.com/doi/10.1002/jcc.24252/full).
In this specific case, I plan to follow whatever instructions the editor provides. In general though, is it better to avoid using personal pronouns in the abstract for scientific writing?