How can u make that judgement without knowing his/ her soil Composition or feeding or knowing if the plant needs it? Or what the compost is predominately composed of? What if it's a compost pile with layers of lawn clippings and now he's mixing a nitrogen rich compost onto a plant going into flower. I think there is just a lack of info to make that call. I'm just a noob so if I'm misinforming him/her please let me know because I would hate to ruin someone's plants because of my lack of knowledge.
Yeah, you sound like a guy, who's been growing only one thing... cannabis, so your gardening experience is quite limited, and don't take this as an offense please. For example, compost I'm using has been checked beforehand on all possible vegetables and herbs, which were also grown without it, and I can tell you straight away that compost doubles, and sometimes triples the growth. You really don't have to spend shitloads of money to analyse your soil in the lab, it's enough you watch how it influences plants in your garden. How do you think farmers have been doing it before technology came in? Oh man

Another thing, there's no way of causing nitrogen toxicity in cannabis with compost, even if it's used without cutting it with other agents, cause this is not a salt-based fertilizer!!! On the top of it, compost usually has NPK of 0,5-0,5-0,5, and often less, so it's not only totally safe, but it's perfect for growing virtually everything.
I'll add that I grow bonsai plants in a soil mix, which is 70% compost with some other organic additives, and I also use BUCKETS of it to grow my jungle plants. You wannna see the effect? There you go.
Some plants that I'm running this season
My bonsai budz
Please, stop scaring young growers, man :tokin: