While the top answer above is excellent, I would go beyond saying it is "acceptable" or "preferred". I would say you "must" use an apologetic tone for one very good reason: if the user is making a mistake, it is because the user does not understand the rules or logic of the system. That is not the fault of the user! It is responsibility of the system to accurately explain the logic of the system to users. A user error then is a mismatch between what the user thinks should be done, and what the system allows to be done.

While one would never be this wordy, if we spell it all out, your apologetic error message is: "I'm sorry that the user interface of this program, your past experience with it, or experience with other similar programs, have led you to believe that you could take such an action at this time, but you can't because ...."

Specific to the case mentioned: the user thought that access might be available. You are apologizing for the misunderstanding that the user had, because the system had not previously communicated that the permission was not available.

What does it mean to say that an error might be the user's fault? Users don't go and do things that they know will not work (that would just waste their own time). The only reason they do something wrong is because they don't know it won't work. If the user does not know something, isn't it really the fault of the system for not making this transparent? Regardless of how obvious a programmer might think it is, the vast majority of the time a mistake is the fault of the system, so write your error messages in accordance, and you will have happier users.

While Mervin's answer is excellent, I would go beyond saying it is "acceptable" or "preferred". I would say you "must" use an apologetic tone for one very good reason: if the user is making a mistake, it is because the user does not understand the rules or logic of the system. That is not the fault of the user! It is responsibility of the system to accurately explain the logic of the system to users. A user error then is a mismatch between what the user thinks should be done, and what the system allows to be done.

While one would never be this wordy, if we spell it all out, your apologetic error message is: "I'm sorry that the user interface of this program, your past experience with it, or experience with other similar programs, have led you to believe that you could take such an action at this time, but you can't because ...."

Specific to the case mentioned: the user thought that access might be available. You are apologizing for the misunderstanding that the user had, because the system had not previously communicated that the permission was not available.

What does it mean to say that an error might be the user's fault? Users don't go and do things that they know will not work (that would just waste their own time). The only reason they do something wrong is because they don't know it won't work. If the user does not know something, isn't it really the fault of the system for not making this transparent? Regardless of how obvious a programmer might think it is, the vast majority of the time a mistake is the fault of the system, so write your error messages in accordance, and you will have happier users.

While the top answer above is excellent, I would go beyond saying it is "acceptable" or "preferred". I would say you "must" use an apologetic tone for one very good reason: if the user is making a mistake, it is because the user does not understand the rules or logic of the system. That is not the fault of the user! It is responsibility of the system to accurately explain the logic of the system to users. A user error then is a mismatch between what the user thinks should be done, and what the system allows to be done.

While one would never be this wordy, if we spell it all out, your apologetic error message is: "I'm sorry that the user interface of this program, your past experience with it, or experience with other similar programs, have led you to believe that you could take such an action at this time, but you can't because ...."

Specific to the case mentioned: the user thought that access might be available. You are apologizing for the misunderstanding that the user had, because the system had not previously communicated that the permission was not available.

What does that mean to say that an error might be the user's fault? Users don't go and do things that they know will not work (that would just waste their own time). The only reason they do something wrong is because the don't know it won't work. If the user does not know something, isn't it really the fault of the system for not making this transparent? Regardless of how obvious a programmer might think it is, the vast majority of the time a mistake is the fault of the system, so write your error messages in accordance, and you will have happier users.

While the top answer above is excellent, I would go beyond saying it is "acceptable" or "preferred". I would say you "must" use an apologetic tone for one very good reason: if the user is making a mistake, it is because the user does not understand the rules or logic of the system. That is not the fault of the user! It is responsibility of the system to accurately explain the logic of the system to users. A user error then is a mismatch between what the user thinks should be done, and what the system allows to be done.

While one would never be this wordy, if we spell it all out, your apologetic error message is: "I'm sorry that the user interface of this program, your past experience with it, or experience with other similar programs, have led you to believe that you could take such an action at this time, but you can't because ...."

Specific to the case mentioned: the user thought that access might be available. You are apologizing for the misunderstanding that the user had, because the system had not previously communicated that the permission was not available.

What does it mean to say that an error might be the user's fault? Users don't go and do things that they know will not work (that would just waste their own time). The only reason they do something wrong is because they don't know it won't work. If the user does not know something, isn't it really the fault of the system for not making this transparent? Regardless of how obvious a programmer might think it is, the vast majority of the time a mistake is the fault of the system, so write your error messages in accordance, and you will have happier users.