Why is "man" not recommended?
"Her serveres man aften kl. 22.00" and "Her serveres aften kl. 22.00" may very well be equal good depending on the situation.
"Her serveres man aften kl. 22.00," tenkte han surt.
"Her serves aften kl. 22.00," informerte hun gjestene sine.
In the first sentence "man" is used in a negative way and if that is the meaning no teacher should recommend that "man" is not used.
Some claim it is too impersonal although I find that a better argument is that it puts more focus on the wrong element of the sentence.
When you say "maden serveres" which is a genuine passive the receiver automatically has his focus on the food "mad" whereas the senctnce "man serverer maden" food has suddenly become the object - we don't have a passive any more, and the receiver automatically attempts to picture who "man" is. This is not what you want him to. That is a relatively unimportant information.
"Man" is rather for a sentence like "I Kina spiser man hunde" (almost like the famous film title). Here you don't want the receiver to have much focus on the dogs; you want to point out that it is general usage in China to eat dogs. To gether with the adverbial "i Kina" the subject "man" gives a relatively clear picture. Personally I think that "man" without any such supplementary info builds up a very vague picture.
But it is also a matter of taste. Not all people can or desire to express themselves with that degree of exactness. But it is an option.
This sentence is pretty clever I think - and it would also work in Danish (exept for a few tidbits):
"Her serveres man aften kl. 22.00," tenkte han surt.
In Danish it would be: Her serveres man om aftenen kl. 22.00
But it differs from the other variations - if I am not mistaken, it is the only one of all examples in this thread because it has neither a subject nor a direct object. The verb, as you see is a normal -s passive and "man" is the indirect object. The rest are adverbials. So this is not really the "man-passive" I am referring to. The dangerous thing in Danish, however, is that there is nothing that marks a word as a dative case.
The same sentence i a different context could be:
De to missionærer lå bagbundet i hytten.
"Jeg har set kannibal-høvdingens spiseplan."
"Hvad stod der på den?"
“Her serveres man om aftenen kl. 22.00."
"..."
Here "man" has become the subject without changing the sentence the least bit.