This looks like some debugging print. Is it needed?

Minor: not sure if worth adding dates like "28 March 2022" to the comments.

It would be much easier to review if everything below would not change indentation, I guess, i.e.

# If attempting to load a point cloud file as mesh, import as verts instead and bail out
if self.use_verts:
    mesh = load_ply_verts(self, filepath, ply_name)
    return mesh

uvindices = colindices = None
# ...

I don't think MP Comment - below comments are left from stock importer comment is needed

Why specifically it's not a vertex color, but instead an attribute with this Col name?

Also I think some sort of "vertex/color handling" is being redone inside blender codebase as we speak (I've seen commits with some sort of "sculpt/vertex color unification" thingies happening just a week or two ago). Does that affect the choice of a custom attribute vs. vertex color by chance?

Not a python performance expert, but wondering: this is a loop over all the vertices. Would it make it faster to move a subexpression like newcolor.attributes['Col'] outside the loop, so that it would not have to search for that attribute, for each vertex, three times?

For headings blender typically uses title caps, although I'm not sure why this is even necessary.

The patch description doesn't mention why this panel was added.
Unless it's essential I'd prefer user interface improvements be committed separately.

This doesn't seem necessary.

Don't pass in self argument, pass in individual arguments instead. Using vertices can be returned instead of setting the operator property.

Prefer not to include these comments, such issues could be resolved in a cleanup pass - or suppressed.

I'd prefer not to pass in "self", as it's not clear which properties are used, also it's possible for the properties to be modified. Instead, pass in the arguments which are needed.

Again, no need to pass in self.

It seems unnecessarily convoluted to have the responsibility of object creation be different for vertex loading. load_ply can create the object in both cases.

The return value from this should be used instead of accessing it by name every time.

The this block does some odd things.

• Access is a mesh which already has a variable assigned.
• Uses the variable name newcolor for mesh data.
• Excesses the color layer for each color channel.

... all these things can be changed a fairly easily.

No need for surrounding parenthesis.

Don't think it's necessary to include this because blender doesn't support per vertex UV coordinates (and isn't likely to).

Don't pass in self