What is not a reason for refusal, so you can stop worrying about it

Short answer: Much of what students lose sleep over appears in no rule at all. This page exists because the worry itself does damage, and because anxious applicants make worse decisions.

Nothing in the official documents makes any of these a ground for refusal

• A passport with no previous travel. No source I found treats a lack of travel history as a problem for a student visa. V21 is honest about the limits of what I know, but no rule names this.
• Studying in a small city rather than Milan or Rome. The rules are national.
• A public university rather than a private one, or the reverse.
• Your family not being wealthy. The rule is a documented amount from a lawful source, not a level of wealth. Bangladesh is on the list of particularly poor countries for fee purposes, which is a benefit rather than a flag (B18, M22).
• Being a woman, being married, or being a parent. Marriage changes your document list (M34), not your standing.
• An IELTS score above the floor but below what you had hoped for. The visa requirement is IELTS 6 (V20). A 6.5 is not a weak application.
• A course that is not prestigious. The rule is that the course fits your background (V19), not that it impresses anybody.
• Not having contacted a professor, if you are a bachelor's or master's applicant. That belongs to PhD applications (P11).
• Being nervous in an interview. Anxiety is not a finding about your intentions.

What does appear in the official framing

Short and unglamorous: a pre enrolment that is not validated, which is an automatic refusal; funds that are insufficient or unexplained; a course that does not fit your background; doubts about documents; language below the required level; and migration risk, which is the judgement one (V16).

The useful conclusion

Spend your energy on that list. Most of the anxiety circulating in Bangladeshi student groups is about things no rule mentions, and worrying about them costs you the attention the real requirements need.