Who decides whether I will be able to open my current documents in ten years? In most cases, the answer is not us. A few months ago I decided that, in my case, it was no longer going to be that way. This is not technological purism, but a practical decision about where my ideas and creations live and who controls access to them.
An open format is one whose specification is public and free. It does not belong to any company. It does not require a specific piece of software to read it. Plain text, Markdown, CSV, SVG, HTML: any basic editor understands them, any operating system handles them, anyone can work with them without asking permission from anyone.
A closed format, by contrast, is a box whose key belongs to someone else. You can use it while the owner wants you to use it, under the conditions the owner sets, at the price the owner decides. The content is yours; access to it, not entirely.
The habit of creating in open formats does not require giving up anything essential. Markdown lets you write with structure without thinking about typefaces or margins. SVG and Mermaid solve diagrams any browser can render. A CSV is more honest and more durable than any proprietary spreadsheet for data that does not need complex formulas.
The initial friction exists. Changing habits always costs something. But it is friction you pay once, unlike a dependency you pay indefinitely: in money, in broken compatibility, in hours lost migrating or converting files.
The ideas are yours. The content is yours. It makes sense for access to be on your terms.