Are sidewalks considered common areas?

What are in other HOA's documents doesn't mean it's in yours. ALL HOA's are separate. If your documents are silent on sidewalks, then call the city to see their stance. That should give you a direction on how to keep going.

BasG are you in a gated community? likely yes the sidewalks are a common element. Even IF you are not in a gated community, the sidewalks could be a common element. The only way to determine that is to look at the plats to your property at the county accessors office.

I'd contact your city first. If the HOA documents are not clear, there's a good chance your board doesn't know either (or only thinks they know).

Take a look at your property survey and the plot plan for the subdivision. The four corners of your property survey (or how ever many corners you may have based on the actual design of your lot" are showing you what property is actually yours. This is the only property that you should be paying taxes on, so also check with county and or parish to make sure of the physical dimensions / size of your lot. If the side walks are not within your property / lot, the side walks are not yours! If the sidewalk is not your property, you are not responsible to maintain, nor to pay property taxes for this property, nor to insure this property. This property most likely is owned by the H.O.A. or the developer or possibly the city, the county and or the parish. Your driveway is your legal "right of way" onto your property / lot. If your H.O.A. and or developer and or H.O.A. management company will not provide you with legal documentation relevant to clarifying this "legal" matter, you would need to do some discovery work with the clerk of courts office within your city, county and or parish to find out "whom" actually owns and is responsible and liable for this property.