When and how should a layperson declare their achievements?

I have on occasion seen commenters here and elsewhere who declare their achievements, such as being a sotāpanna. These comments are downvoted, so they do not appear to be appreciated. If comments like these show up on public forums then casual visitors may themselves see that the path can be followed, that people living today have found that the teachings work, and may themselves be inspired to study the Dhamma. That would be a good possible outcome from such comments. So is it considered wrong to write such declarations publically (at least if one is not a monk) and when would be the appropriate time and place to make declarations of achievements?