I notice that some authors describe their siddhis in the preface of their books. Similarly, some teachers describe them as a part of their classes. Howeve, it is clear from their statements that they are doing this as a part of their advertisement.
Mentioning of one’s siddhis may be acceptable or recommended in a certain context. e.g. one is saying that it is possible to lift the entire Mount Diablo, and then mentions that he has lifted the Mount Diablo ten years ago, such and such persons were present, and their names are x,y,z and their phone numbers are phx, phy, and phz. In this case, this person wants to encourage people to build strength and tell them that it is possible for one to obtain such a siddhi. This is one example. Their may be other acceptable examples.
However, if one is doing this as a part of advertisement of their product, it becomes somewhat confusing. If one is having a profound siddhi, he/she may of course be able to do lower level chore much easier. For example, if one can lift Mt. Diablo, so hopefully, he/she will be able to lift a couch single-handedly. Now, if this person wants help from friends to lift one couch and makes use of the statement about his lifting Mt. Diablo, that would seem strange indeed.
Also, another thing is that when one mentions their power, some kind of proof will be demanded by the audience. If this proof is not there, it will create problems even if the actual power is true.
And, there is also a question whether such a power is needed for a given task. For example, recently I saw one book that states that the author hears voices from the age of 4. Now, using this voices, he advises people about what diet they should take for various ailments. The book that he wrote about the foods for various ailments is a beautiful collection of foods indeed. However, those foods are the ones that are recommended in many a nutritional circles of today. So, the question arises whether the power is needed for such a knowledge.
Anyway, I wrote my thoughts. You may have your own. But, from the study of Yoga, I can say that getting such powers using meditation is a formidable task and with that energy spent, possibly, one can get many wonderful things.