Is it acceptable to cite people without putting the appropriate diacritics in their names? I've begun preparing my thesis and several key papers in my field are written by people with foreign accents in their names. While I have found a way to include this in my thesis with BibTeX. However it has come to my attention that many citations exported from online journals (as .rif, .enl, or .bib) or my previous EndNote library may not include accents in non-English names. 

While I would like to attribute these appropriately it is clearly a laborious task to check for the sheer number of references included in a thesis unless strictly necessary. Therefore I have two related questions:


Is it acceptable academic conduct to cite authors without correct accents when citing them in an English language thesis (or publication)?
Is it common practice for reference managers or online export tools to support accents or author names (i.e., can I take it for granted that my existing library has included these characters correctly or will be necessary to check references previously imported by online databases)? 


To clarify, this query concerns accents such as those found in names originating in French, Italian, Spanish, Hungarian, German, Scandinavian and Te Reo Māori languages. Such as the symbols:

ó, ò, ő, õ, ø, ö, and ō
I'm not sure how far ethics comes into this, but omitting accents is, effectively, a misspelling of the name. If you need to cite something by Schön, and you instead write "Schon", I'd regard that as analogous to writing "Schöm" or "Schöh": pretty close, but certainly a typo. If I'm reviewing a paper, I will request correction of missing accents as I would for other misspellings, but I wouldn't regard it as an ethical breach.

In practice, there's a bit more leeway for missing accents than for other misspellings, partly due to former limitations in computer typesetting, and partly due the dominance of English as a scientific language and the frequent belief among native English speakers that accents are always optional. As Burak Ulgut says, some authors won't mind missing accents, while others will care a lot -- but since you can't know which is the case for any particular author, you should keep the accents. In some cases, missing an accent may have unfortunate consequences in the author's native language: if you cite a Swedish Dr Hörberg as "Horberg", you've just turned them into "whore mountain".

For citation purposes, the correct spelling is (almost always) the one on the publication itself: if, say, Miloš Blažek chooses to publish as Milos Blazek then that's how you cite him, no matter what it says on his birth certificate.

On the technical side: unfortunately you cannot take it for granted that exported bibliographic records will handle non-ASCII characters correctly, or for that matter that they will handle anything correctly. Bibliography record formats are a mess of partially supported, poorly defined standards interconverted by buggy code, and you should always eyeball the record after importing it to catch any errors (not only accents).

As you say, it's clearly a laborious task, but so are many aspects of writing a thesis :).