Absolutely riveting fact about adverb placement after modal verbs

I just thought you'd like to know, this copy and paste from a website changes where I thought adverbs go in a sentence when using modal verbs. Exciting stuff:

here are a number of adverbs that normally appear as part of the complex verb. The ones you mention, "just," "always," and "never," are some of the most common, but many adverbs of frequency (words that express how often something happens) follow the same rule. Generally, these adverbs come after the first auxiliary in the complex verb:

1) John has frequently been seen at the club.
2) Martha can often be found in her garden.
3) Peter said that he will rarely be going to concerts this year.

There are a few other adverbs that occur in this first post-AUX position that have nothing to do with frequency: "just" and "ever" are the most common. In addition, adverbs of manner can optionally occur after the first AUX (as in this sentence, after "can").