Honestly, I haven't heard the platitudes that most people have direct experience of outside of hearing other people talk about them online, and I am extremely fortunate for that as it probably would've led my thinking to spiral even further if someone directly said it to me.
With that context, I'd say the... not stupidest or worst thing, but the weird advice and expectation that I'd get rid of my suicide paraphernalia or put them out of reach when I brought up my thoughts in therapy. Of course, they never knew what exactly I had access to because I wasn't willing to tell them, so I just played it off as the conventional methods someone would use to attempt suicide (ODs, crashing a car, etc.) rather than actually telling them I had the means within my reach.
Strangely, having them around still provides a comfort, even if I don't end up using them. Again, the advice/expectation wasn't stupid or bad, it just feels it wasn't proportional to my circumstance at the time. It still isn't. I despise the term, but, for lack of a better word, I wasn't a "common" suicidal case of someone who would attempt because they had the means within their reach. I wasn't a case of someone at the level that they would just give up their methods because they feared taking their own life and wanted to get better, despite any character of such I may have been exuded in my responses. I'm not a special case, there are plenty of people here that have been in similar mindsets and situations, but it wasn't a "common" case that could be fixed my merely stating the person should remove the methods from their reach either.