So, I was looking at one of the example sentences given i.e.
わたしはコウイチの意見に同感ですね。
I empathise with Koichi’s views.
Empathy being a suru verb, could you not equally say this (formality aside, though it is likely the type of thing one would say more carefully and so perhaps more formally, I suppose!)? Or does this yield a different connotation? Or perhaps it plainly doesn’t have that sense, because I haven’t looked at grammar for a while.
わたしはコウイチの意見を同感するね。
I empathise with Koichi’s views
Well it depends pretty much entirely on the word yeah, but since you’re asking about likelihood I can still give you an answer. を is the more commonly correct one, so if you gotta guess then I would go with that one.
There are a handful of verbs that use に and not all of them for the same reason. There are plenty of sites that explain some of the differences that you can use
My personal advice is to honestly do what you want when it comes to studying it, but know that (imo) this can be a pretty tricky subject for beginner and intermediate. If you don’t get it 100%, I wouldn’t sweat it and would honesty just leave it up to your brain to notice patterns on its own. Some verbs that use に that seem like they should use を will make a lot more sense when you can understand the japanese definition like 憧れる.
