Harassment in the workplace isn't what we may generally consider to be harassment in out personal lives. The term "hostile
work environment" comes to us from the Supreme Court of the United States. It is a very specific term. The high court required another ingredient beyond the types of things you are talking about here.Hostile work environment is illegal harassment (ingredient 1) which is based on race, religion, gender, age, disability or FMLA
use (ingredient 2). Without that second factor, there can be no hostile work environment. Additionally it must be unwelcome, sever and persistent. In your situation you don't make mention of what the conversations alluded to. However, if they didn't involve age, race, sexually charged, ethic etc. conversations, then first off they are totally irrelevant to "harassment" in the employment context. Second, if the employee participated in these discussions without it bothering him/her - to this extent they are welcomed (and they went on for a year without him saying anything), lastly, if they only happened infrequently and were about mundane things - they were neither persistent or severe enough to be actionable. So this is how'd I'd recommend handling the matter. Write the truth in your statement, but emphasize how the conversations didn't involve race, religion, gender, age, disability. Also emphasize that they were welcome - that the employee participated in them and didn't seem to be bothered at all. Lastly, if it is the case - write how the conversations ony happened infrequently and emphasize that they were not severe in terms of language used.