I am glad that you found my code instructive. I regret my laziness in leaving the uninformative letter c_ when I could have written the more revealing positionOfDecimalPoint_. It took me some time to figure out the output of RealDigits when applied to rational numbers. The documentation on that has room for improvement.

The recurring digit sequence seems complete to me. From RealDigits[130/7] you get {{1, {8, 5, 7, 1, 4, 2}}, 2}, which is equivalent to {{1, 8, {5, 7, 1, 4, 2, 8}}, 2}. The sequence lends its first digit to the pre-recurring sequence and gets it back at the end.

As for the underscore, yes, now that I think of it it is indeed unexpected that Overscript[3, Blank[]] should work. I really meant to write underscore, not Blank[].

What is wrong with 130/7? I simply arranged for the ovlerline non to cross over the decimal point. I was not aware of OverBar, which is indeed shorter. However, Overscript is regularly documented. Curiously,

OverBar[x] === Overscript[x, _]

gives False, but if you evaluate

{OverBar[x], Overscript[x, _]}

and look at the underlying BoxData in the output cell, you will see that they are represented identically as OverscriptBox["x", "_"]. If you copy and paste one of them into an expression that expects the other, you may run into mysterious trouble.

What is wrong with 130/7? I simply arranged for the ovlerline non to cross over the decimal point.

That's the problem: for 130/7 the recurring digit sequence is incomplete, hence the output is wrong.

The output from RealDigits is complicated to use. Here is what I came up with:

normalizeDigitSequence =
  {{{beforeRecurring___, {recurring__}}, c_?NonPositive} :>
    {{0, beforeRecurring, {recurring}}, c + 1},
   {{beforeRecurring___, {recurring__}}, c_?Positive} /; 
     Length[{beforeRecurring}] < c :>
    {{beforeRecurring, First[{recurring}],
      RotateLeft[{recurring}]}, c}};
addOverlineToRepeating =
  {{beforeRecurring___, {recurring___}}, c_?Positive} /; 
    Length[{beforeRecurring}] >= c :>
   Row[Append[Insert[{beforeRecurring}, ".", c + 1],
     Overscript[Row[{recurring}], _]]];
RealDigits[13/7] //. normalizeDigitSequence /. addOverlineToRepeating

This is meant for display only. It does not evaluate to a number.

Instead of using the undocumented (?) Overscript with a Blank as a second argument, one can also use OverBar.