Coding style
I usually edit more code others made, than I create new files, and while most of the code is in PHP, there’s a huge difference in the coding style applied by different developers, and some styles are much more annoying than others. I do respect that people are different and that is probably more efficient to allow for some degree of personal style than to try to enforce a single common style. If possible try to make standards where all can agree upon them, and where it isn’t possible, don’t force it too hard (on less pressing issues makes it necessary).