What pronoun should theses use? It is generally courtesy to use the plural 'we' or 'our' in papers, even when the primary author was the only contributor. While using personal pronouns in academic papers is typically a very bad idea, I have seen them being used in theses. What gives? Technically a PhD thesis is only meant to be the candidate's work, but if this work features previously published work surely you'd expect to same rules to apply to the thesis as applied to the academic papers?

So in terms of professional appearance and etiquette what is the (typically) correct approach? Should personal pronouns be used in a thesis?
I used “we” (except for the acknowledgements). It’s what I’m used to when reading academic writing. Anything else wold seem weird to me.

Although the primary reason was that It was a stapler thesis and that is what the papers I was copying from used. It would have been too much effort to change it.

Customs may vary by field and country. The best thing to do is look at a few theses coming from your department and copy their style.