Ooo, that is a particularly great example - I wouldn't have thought of that (no pun intended), and I pride myself on being able to scale my use of English to the skill-level of the person I am speaking to.

In fact, even if I was in "speak simply" mode, I would still use "would" instead of, perhaps, "recommend," as "would" is a shorter word: I favor simpler words over multi-syllable versions when trying to be maximally understandable to someone whose native language is not English. I'm glad you brought it up!

To this day, I'm still unsure whether there was a misunderstanding or if I was being taken advantage of, but I presume good intent from the person.

Sometimes people just hear what they want to hear. I’ve definitely been in situations where my advice was carefully caveated with a precursor “If I were in your situation, I would do X” and the person has just heard “I would do X”.

"I suggest ..." or "[Maybe] try ...".

As a non-native speaker, I fail to see how that can be understood differently.

Which meaning of it do you feel is the one that is clear to you?

I understand it as an advice, recommendation - "If I were you, I would do X".

After re-reading I probably see the issue, but you never said "I will do X" which changes to would in reported speech:

I will do X -> You said you would do X.

Did they understood "I would do X" as "I will do X"?

I would never understand it as "but you said you would do it", I would say "would" is safe to use with non-natives. But it may depend on the native language of the other person. There are some really weird languages out there!

The other day Duolingo did show me you can say "и A и B" ("и" being "and") to say "both A and B". Start a sentence with "and", a conjunction, without anything before to... "conjunt"... I still can't parse it without raising an exception.