Sometimes a disagreement gives me pause to explore how I see a certain style of writing and why. In this case, a member of my critique group and I differed on the use of italics for inner dialogue, or thoughts. He hates them. I use them. It has caused some strong discussion. (Yes, we remain good friends.)
Basically, how you approach a character’s thoughts comes down to personal preference unless your work is going to a publisher with a strong editor and/or a strong style sheet.
In my novel Conjure Woman’s Cat and its two sequels, I used italics to indicate that the cat was using telepathy to talk to the conjure woman. My editor thought I didn’t need to do that, but I didn’t want to go through entire pages of “thought speech” with “Lena thought” and “Eulalie thought” tied onto all the lines. That might make readers think they were just thinking about those things when they were communicating them.
Italics becomes a bit of a problem when passages become lengthy. It’s generally considered harder to read–or a “put off” to readers–when it covers entire pages.
This piece in Indies Unlimited is, I think, a catalyst for us to think about what we’re doing when we write.