It may 'obviously' be an opinion, but when you use a word (the word 'is') that is linked the stating fact, not opinion, there's no playing of words involved. It's simple English. If you want to talk on a board where discussions are taking place all the time, it's best to use the language used on that forum in a proper way to make yourself 100% clear, so people know exactly what your saying. You mean to convey a feeling, but you do it in a way that is used to state a fact. Ofcourse some people are going to be confused about what you want to say.
If a person becomes confused between opinions and claims of fact without constant reminders I'd say it's more of a problem on the reader's side than the writer's. You'll notice that successful movie critics don't have to sprinkle their reviews with phrases like "in my opinion," "as I see it," "I think" and so on, which would not only be repetitive but is so obvious as to go without saying. I think most readers of this board are familiar enough with that type of writing to not be confused.