Yes and No. That is the answer you are going to get depending on who you talk to. There are several different ideas about foods and what to avoid when dealing with UC. Some people say that potato is completly 100% OK to eat whenever you want to if you have UC. Others say it is a starch and not good to eat to treat UC.
Some of the answer depends on how you plan to treat your UC. If you are treating your UC successfully with medications, than it might be alright to eat potato when you like. I would still eat it in moderation compared to other things.
But, if you are like me and follow a specific carbohydrate diet, the SCD diet, I avoid potato nearly 97% of the time. Of course I slip in a few french frie every once in a while, but I am not sitting down and eating a whole baked potato ever anymore. For me, the potato which is something I used to eat all the time prior to being diagnosed with UC is something I just try to avoid.