The answer to this question is, unsurprisingly, yes. While bold, underlined or italicized texts have been around a long time, and give visual cues as to their functions, purposes or emphases, online publishers including bloggers have much more choice. Therefore it’s much easier to be very emphatic about something. It is even tempting to do so. Adding a bit of colour helps to draw in the reader. However, there is a tendency to go overboard with various font faces, colours and sizes.
Different sites have different needs and there are no absolute rules. However, one thing that will turn me off is the excessive use of different text styles, seemingly without purpose. It is a bit like overusing exclamation marks!!!!! It doesn’t look good, and it doesn’t look cool. Abrupt changes of style break the flow of the text and I find them distracting and disruptive.
May be this is some sort of ingrained conservatism in me, or that I’m used to reading printed text more than online publications. It may even be a generational thing. But whatever style one adopts, the text must be legible. There ought to be enough contrast between the background and the text colours, and the font should be sufficiently but not excessively large, to ensure the visitors can read the content.