When rows/columns are frozen, adjacent "hidden" comments can become invisible - when mouseover happens, they can't be seen. Even without the invisibility that freezing rows/columns can bring, it would be preferable if the user could set the size and position configured when a comment is shown would persist when it's hidden, to preserve its visual relationship to other elements in the sheet.
For example, a comment on a cell in column B appears on mouseover. But if freeze columns/rows is applied at the border betweein columns B & C, mouseover does not make the comment appear. This is true even if, when the comment is not hidden, its location is moved to cover column A. In addition, when freeze columns/rows is not activated, there is an issue with comment location. When a comment, hidden by default, is changed with "show comment" and then relocated and/or resized from its default position and size, that position and/or size is not respected when the comment is again hidden with "hide comment". Mouseover pops the comment in its default position and size. So, the request is that comments operate as expected/desired: they appear on mouseover, even if the column is frozen; and they appear on mouseover where they've been located, and sized as they've been sized. I consider this to be a bug, because a reasonable expectation about comments being visible on mouseover is violated, and because it's also a reasonable expectation that hidden comments retain the size and position set while not hidden, when they are made hidden. As things stand, hidden comments often do not appear correctly -- or at all!