Some webmasters claim putting your keywords in bold or putting your keywords in italics is a beneficial ranking factor in terms of search engine optimizing a page.

It is essentially impossible to test this, and I think these days, Google could well be using this (and other easy to identify on page optimisation efforts) to determine what to punish a site for, not promote it in SERPs.

Any item you can ‘optimise’ on your page – Google can use this against you to filter you out of results.

I use bold or italics these days specifically for users.

I only use emphasis if it’s natural or this is really what I want to emphasise!

Do not tell Google what to filter you for that easily.

I think Google treats websites they trust far different to others in some respect.

That is, more trusted sites might get treated differently than untrusted sites.

Keep it simple, natural, useful and random.