https://github.com/t-edson/SynFacilSyn is quite comfortable for your own syntax.
I used it once for NetherPascal here on the forum.
There is good documentation in odt format and you can basically copy over one of the examples and just write a small xml file with the syntax description.
It is much more configurable than SynAnySyn and just as easy to use.
Very easy to configure single and/or multiline comments as you like.
In your case this would work:
<Comment Start=";;" ></Comment>
This is a single line comment definition.
[edit]
do not use: the package SynFacilSyn is currently not in a compilable state with trunk..
I did not know that, until I tried to compile my old example.