Should there always be a comma after "therefore","However" etc.?

Solution 1:

Not really. There are many cases for which a comma is unnecessary.

He is strong, and therefore a likely candidate.

However strong he is, he is not a likely candidate.

And so on.

As for subordinate clauses, where the words function as subordinating conjunctions, the comma isn't always necessary either.

He is strong, therefore he must be a likely candidate.

Still, I would use one with however in that case:

He is strong; however, I don't think he's a likely candidate.

Note the semicolon. A period would work there as well. This is because "however" doesn't really work as a subordinating conjunction. Therefore isn't usually classed as such either, but I believe it can function as one just fine.

Solution 2:

This is a problematic area, because the modern tendency is to omit commas wherever this can be done without prejudicing meaning and/or readability.

By their very nature grammars and style guides tend to be somewhat behind the times. Who can say whether I 'should' have inserted a comma after nature in the preceding sentence?

I suggest that as a rule of thumb, if you can reasonably speak the sentence without a noticeable pause after the word however, don't bother with the comma. Otherwise, use it (same rule applies to otherwise, obviously, but these things are never cut-and-dried).

Solution 3:

I found this here (ncsu.edu).

Chicago Manual of Style 5.69: "When [transitional adverbs] are used in such a way that there is no real break in continuity and no call for any pause in reading, commas should be omitted.

Chicago gives four examples: (1) The storehouse was indeed empty; (2) I therefore urge you all to remain loyal; (3) Wilcox was perhaps a bit too hasty in his judgment; (4) Palmerson was in fact the chairman of the committee.

Solution 4:

Should there always be a comma? No.

Should there often be a comma after linking adverbials? Yes.

Will you and others consistently add a comma? No.

Why? Because English is losing its commas and, although the comma's death is mourned by some such as myself, many English writers seem to be happy to dispense with it. Language changes. Punctuation in written English was developed to aid in oral reading to help indicate where and how long to pause. As most reading is silent now, the need for it is dying a slow death. Look at the semicolon. It's on its deathbed now. The comma is not far behind. The truth is that it's rarely necessary. It helps in some lists (note the Oxford comma debate) and in some clause structures, but in those situations where it's not absolutely necessary to aid in creating meaning, it's disappearing.

Solution 5:

Commas should be used in a similar way to a rest in music. The rest is silence, however the rest can be replaced by extending the value of the note, for the flow of the music. I use commas with breathing in mind. I read my text many times, next I omit or insert what is applicable to create a comprehensive written statement. Writing should flow, as a melody would.