Not sure why this needed to be a new thread since a quick search reveals multiple duplicate threads.
Because it is FT, there is never a concensus. But, if you skim some of these and there had to be a vote, it would probably come out that you recline slowly, perhaps just a bit for 5-10 seconds and then all the way. That is fair enough warning. If the person behind you then reacts and perhaps asks for a minute to readjust his laptop or whatever, that seems reasonable. But, there are very few who believe that one needs to give verbal notice or consult.
In fairness, a properly constructed tray table should be hinged so that the position of the seatback does not affect its level.